The Development of a Qualitative Protocol to Analyse the Tackle in Rugby Union Football

Trevor N. Savage

A thesis submitted in fulfilment of the requirements for the degree of Master of Science

School of Risk and Safety Science Faculty of Science University of New South Wales Australia

August, 2011

ii ORIGINALITY STATEMENT

I hereby declare that this submission is my own work and, to the best of my knowledge, it contains no materials previously published or written by another person, or substantial proportions of material which have been accepted for the award of any other degree or diploma at UNSW or any other educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project's design and conception or in style, presentation and linguistic expression is acknowledged.

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iii COPYRIGHT STATEMENT

‘I hereby grant the University of New South Wales or its agents the right to archive and to make available my thesis or dissertation in whole or part in the University libraries in all forms of media, now or here after known, subject to the provisions of the Copyright Act 1968. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation.

I have either used no substantial portions of copyright material in my thesis or I have obtained permission to use copyright material; where permission has not been granted I have applied/will apply for a partial restriction of the digital copy of my thesis or dissertation.'

A number of figures have been removed from this thesis because of copyright restrictions. The reference to the figures has been retained.

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‘I certify that the Library deposit digital copy is a direct equivalent of the final officially approved version of my thesis. No emendation of content has occurred and if there are any minor variations in formatting, they are the result of the conversion to digital format.’

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iv ABSTRACT

This thesis describes the development of a protocol to analyse the tackle in rugby union. The tackle is a collision event between a Ball-carrier and one or more opponents. The most frequently occurring match event, it has been consistently associated with a high risk of injury. Quantitative investigations of skill and injury in the tackle are hampered by its multi-factorial nature. A reliable qualitative protocol, prepared through a systematic and repeatable framework, represents a potential method of collecting information to narrow the focus for future investigation.

A qualitative analysis protocol was developed to assess the tackle through evaluation of 107 mostly nominal fields. Fields were developed in consultation with epidemiological data, coaching literature, and applying biomechanical and qualitative skill analysis frameworks to identify aspects of skill and injury. The reliability of the analysis protocol was then assessed in two inter-rater reliability (IRR) studies. The results of the first IRR study were reviewed at a meeting of an expert panel and the protocol was modified to improve agreement before being tested in a second IRR study.

In the first IRR study, substantial agreement (>70%) was obtained in 24 fields. Agreement amongst participants for medical events was almost perfect (91%) and agreement identifying a tackle according to the study definition was 74%. The mean agreement in all fields was moderate (61%). Slight agreement was observed for identifying the body region struck and the direction of travel of the players following the impact. The timing of analysis was identified as a potential reason for poor agreement. The results of the second IRR study suggested that providing a specific temporal reference for observations improved agreement in some fields and substantial agreement was observed in 48 fields. There was still disagreement in some important fields of the protocol. Following operational modifications, the protocol was used to code 6,618 tackles in a larger study of tackling technique and v injury risk. A sample analysis of 100 tackles is presented to demonstrate the utility of the protocol.

Few qualitative technique analyses have described the development of the analysis method or examined IRR following changes to improve agreement. The results of this research indicate that the general agreement between raters using this protocol was moderate, and care needs to be taken in defining the variables used.

vi

“If we ignore the things that we cannot measure, then we cannot fully understand what we are researching” Soshanna Soafer, 1999

“Not everything that can be counted counts, and not everything that counts can be counted” William Bruce Cameron, 1963

vii

An elementary tackle in rugby union involving a Ball-carrier and one Tackler

viii RESEARCH BACKGROUND AND ACKNOWLEDGEMENTS

It was my father who first gave me an interest in the world around me, my daughter who continues to enlighten and inspire me, particularly to ask ‘why’ and my undergraduate lecturer in biomechanics who gave me first the interest and then the opportunity to perform research in this field.

The Rugby Union Injury Surveillance Study (RUISS) was the catalyst for my research and the research of our group in the tackle. The necessity of researching injury aetiology in the tackle evolved from RUISS, for which I was Project Officer at the University of New South Wales (UNSW) between 2002 and 2006. The results of RUISS confirmed the observations of numerous concurrent studies by identifying an apparently disproportionate incidence of injuries occurring during the tackle. During my discussions with the rugby faithful of the Sydney grade competition, conversations with medical staff and whilst collecting match video tapes from the bemused general managers of rugby clubs, it became clear to me that there was a widespread interest in investigating and addressing this problem.

At the time that this research commenced in March 2006, a limited number of studies had measured tackle impact forces and physiological responses to the tackle, but there had been no attempt to describe the tackle event comprehensively. The limitations of motion analysis and obvious ethical restrictions meant that tackle injury could not be investigated in the laboratory using ‘traditional’ research methods. An alternative had to be found. Qualitative analysis seemed well placed for such an investigation because of its flexibility and utility in narrowing the focus of investigation. However there is was also awareness of addressing the perceived bias of qualitative analysis through constructing an analysis protocol that was systematic in both development and application.

This thesis describes the development of a qualitative analysis protocol to analyse the tackle in rugby union. The development of the protocol was undertaken by a

ix research group directed by Associate Professor Andrew McIntosh at UNSW in collaboration with the Rugby Football Union, England (RFU). Criteria to assess tackling skills were developed independently by each group. Following significant investigation, discussion and deliberation, these criteria were combined to instigate a reliable and valid method of analysis for future research. As a member of the research group at UNSW, I was actively involved in the development of the tackle analysis protocol and discussions of the results obtained in the inter-rater reliability (IRR) studies. I developed and co-ordinated the IRR studies under the direction of Assoc. Prof. McIntosh.

I am indebted to the supererogatious volunteers of the Sydney Rugby Community who assisted with RUISS and the tackle study. I also acknowledge the contribution of the RFU team to this project, particularly Dr. Simon Kemp for his interest in my work and friendship. During my time at UNSW I was fortunate to work with very talented and wonderful people. Research can be a hard slog that was often made easier through their camaraderie. My contribution to the work and dynamic of our research group from 2002 and 2008 is a proud achievement in my career. I should like to make mention of my supervisor, Assoc. Prof. McIntosh, and particularly my co-supervisor, Dr. Bertrand Fréchède, for their guidance and support over the entire period and not only the period of candidature. I would also like to thank DEb and Nicole for their valuable comments on the draft thesis. To my other colleagues and friends from the former biomechanics research group and the former School of Risk and Safety Sciences at UNSW, cheers cobbers.

To my family for their love and support, particularly Nicole, who has given up so much and placed many things on hold to join me in Australia, Bridie, my daughter whom I love dearly, and my parents who have contributed much to my person. There have been times where I stared for hours blankly at a computer screen wondering where and how to start and all and sundry have been expected to accommodate the reciprocal effects of hitting the pause button while I got this ‘thing’ done. I hope to repay my debts of patience and inattentiveness.

x TABLE OF CONTENTS

ABSTRACT...... V RESEARCHBACKGROUNDANDACKNOWLEDGEMENTS...... IX TABLEOFCONTENTS...... XI TABLEOFTABLES...... XV TABLEOFFIGURES...... XVII LISTOFTERMINOLOGY...... XIX Rugbyspecificterminology...... xix Tackleanalysisprotocol...... xx LISTOFABBREVIATIONS...... XXI ANINTRODUCTIONTORUGBYUNION...... XXII CHAPTERONE INTRODUCTIONANDSTATEMENTOFTHEPROBLEM...... 1

1.1 WHATISATACKLE?...... 2 1.2 RESEARCHOBJECTIVES...... 4 1.3 RESEARCHQUESTIONS...... 5 1.4 RESEARCHHYPOTHESIS...... 6 1.5 RESEARCHOUTCOMES...... 6 1.6 THESISSTRUCTURE...... 6 CHAPTERTWO INVESTIGATINGTHETACKLEUSINGASPORTSINJURYPREVENTIONFRAMEWORK...... 9

2.1 THESEQUENCEOFSPORTSINJURYPREVENTION...... 10 2.2 ESTABLISHINGTHECAUSEOFINJURY...... 14 2.3 SUMMARY...... 20 CHAPTERTHREE REVIEWOFLITERATURE...... 21

3.1 METHODSFORLITERATUREREVIEW...... 21 3.2 FREQUENCYOFMATCHEVENTS...... 23 3.3 RUGBYINJURIES...... 25 3.3.1 ConsiderationsfortheComparisonofInjuryData...... 25 3.3.2 EpidemiologicalResearchinRugbyUnion...... 27 3.3.3 PatternsofInjuryinRugby...... 34 3.3.4 FoulPlay...... 37 3.3.5 PlayingConditions...... 39 3.3.6 Summary...... 40 3.4 TACKLEINJURIES...... 41 3.4.1 FocussedTackleResearch...... 42 3.4.2 InjurySurveillance...... 46 3.4.3 TackleFrequencyandInjury...... 53 3.4.4 RiskFactorsforTackleInjury...... 55 3.4.5 SummaryandDifficultiesinAnalysingtheTackle...... 67 

xi 3.5 ANALYSINGHUMANMOVEMENT...... 68 3.5.1 AnOverviewofResearchFrameworksforTechniqueAnalysis...... 71 3.5.2 Selectingaframeworkforanalysisofthetackle...... 76 3.5.3 TheQualitativeAnalysisProcess–AttainingObjectivityandAddressingBiasof SubjectiveAnalysis...... 77 3.5.4 ModelsforPreparingaQualitativeAnalysisProtocol...... 82 3.5.5 QualitativeAnalysisofSportingSkills...... 87 3.5.6 QualitativeAnalysisofNonͲSportingMovementTasks...... 99 3.6 VALIDITYANDRELIABILITYINQUALITATIVEANALYSIS...... 102 3.7 METHODSOFASSESSINGRELIABILITYFORQUALITATIVESCALES...... 103 3.8 CHAPTERSUMMARY...... 107 CHAPTERFOUR DEVELOPMENTOFAPROTOCOLFORTHEQUALITATIVEANALYSISOFTHETACKLE...... 109

4.1 METHODS...... 109 4.2 RESULTS...... 114 4.2.1 TackleDefinition...... 114 4.2.2 PreviousResearch...... 115 4.2.3 Developinganunderstandingofthetackle...... 116 4.2.4 Organisingtheinformationcollectedandrefiningtheanalysisprotocol...... 124 4.2.5 Firstdraftofthecodermanual...... 126 4.3 EXPERTMEETING...... 132 4.4 RESEARCHCOLLABORATION...... 134 4.5 SUMMARY...... 135 CHAPTERFIVE TESTINGRELIABILITYOFTHETACKLEANALYSISPROTOCOL...... 137

5.1 METHODS...... 137 5.1.1 ParticipantsandTask...... 137 5.1.2 Training...... 139 5.1.3 Measurementofagreement...... 140 5.2 RESULTS...... 141 5.2.1 Tackledefinition...... 141 5.2.2 Theupperlevel...... 142 5.2.3 Thelowerlevel...... 145 5.2.4 Groundcontact...... 149 5.3 CHANGESTOTHEANALYSISPROTOCOLANDDISCUSSION...... 152 CHAPTERSIX TESTINGTHEREVISIONSTOTHEPROTOCOL...... 157

6.1 METHODS...... 157 6.1.1 Participantsandtask...... 157 6.1.2 Training...... 158 6.2 RESULTS...... 159 6.2.1 Tackledefinition...... 160 6.2.2 Theupperlevel...... 160 6.2.3 Thelowerlevel...... 163 6.2.4 Groundcontact...... 167 6.3 SUMMARYANDDISCUSSION...... 170 

xii CHAPTERSEVEN APPLICATIONOFTHEPROTOCOLTOASAMPLEOFTACKLES...... 173

7.1 METHODS...... 174 7.2 RESULTS...... 175 7.2.1 Completionandoverviewofthesample...... 175 7.2.2 Internalconsistencyofsimilarprotocolfields...... 177 7.2.3 Playersize,tackletechniqueandimpactforce...... 180 7.2.4 Tacklercompliancewithpromotedtacklingtechnique...... 183 7.2.5 BallͲcarriercompliancewithpromotedtacklingtechnique...... 184 7.2.6 InjuryRiskfactors...... 185 7.3 SUMMARYANDDISCUSSION...... 188 CHAPTEREIGHT DISCUSSION...... 191

8.1 SELECTIONOFQUALITATIVEANALYSISANDDEVELOPMENTOFTHEPROTOCOL...... 191 8.2 VALIDATION...... 193 8.3 RELIABILITY...... 194 8.4 OUTCOMES...... 195 8.5 STRENGTHSANDWEAKNESSES...... 197 8.6 CONCLUSIONS...... 200 REFERENCES...... 201 LISTOFCONFERENCEPRESENTATIONSARISINGFROMTHISRESEARCH...... 215 APPENDICES...... 217 APPENDIXA CODINGMANUAL,INTERͲRATERRELIABILITYTESTING,PHASE1...... 219 APPENDIXB CODINGWORKBOOKFORTHEFIRSTINTERͲRATERRELIABILITYSTUDY...... 249 APPENDIXC WORKEDEXAMPLEOFPERCENTAGEAGREEMENT...... 253 APPENDIXD CODINGMANUAL,INTERͲRATERRELIABILITYTESTING,PHASE2...... 257 APPENDIXE GRAPHICALUSERINTERFACEOFLOWERLEVELANALYSISFROMTHETACKLEDATABASE...... 303 APPENDIXF PROPORTIONOFCOMPLETEFIELDS...... 305

xiii

xiv TABLE OF TABLES

Table 3.1:  Search terms used to identify literature for this review...... 22 Table 3.2:  Type of injury definition, cohort and injury incidence rates for injury surveillance studies in rugby union...... 29 Table 3.3: Injury severity in published injury surveillance research...... 31 Table 3.4:  A comparison of the proportion of tackle injuries according to the injury definition used in injury surveillance studies in rugby union...... 47 Table 3.5:  Proportion of tackle injuries from epidemiological studies of rugby union ...... 50 Table 3.6:  Summary of research using qualitative technique analysis and incorporating reliability testing ...... 101 Table 3.7: A scale for interpreting values of the Kappa statistic ...... 107 Table 4.1:  Critical features of technique for the Ball-carrier and Tackler ... 118 Table 4.2:  Skill, environmental and match factors affecting the tackle (using Haddon’s matrix) ...... 124 Table 5.1: An arbitrary scale for assessing percentage agreement, modified from Landis and Koch (1977) ...... 140 Table 5.2:  Agreement rates in Upper level analysis fields for IRR1 ...... 143 Table 5.3:  Observed agreement rates for variables in the tackle type field of IRR1 ...... 144 Table 5.4:  Agreement rates in fields evaluating the tackle impact for the Ball-carrier ...... 146 Table 5.5:  Agreement rates in fields evaluating the tackle impact for the Tackler ...... 148 Table 5.6:  Agreement rates in fields evaluating ground contact characteristics for the Ball-carrier ...... 150 Table 5.7:  Agreement rates in fields evaluating ground contact for the Tackler ...... 151 Table 6.1:  The number of tackles identified in IRR2 including tackles correctly identified according to the study definition and other events that were not tackles according to the study’s definition ...... 160 Table 6.2:  Agreement rates in Upper level fields for IRR2 and percent change (IRR2/IRR1) ...... 162 Table 6.3: Agreement rates in fields evaluating the tackle impact for the Ball-carrier ...... 164 Table 6.4: Percentage of agreement in fields evaluating tackle contact for the Tackler ...... 166 Table 6.5: Agreement rates in fields evaluating Ball-carrier ground contact ...... 168 Table 6.6:  Agreement rates in fields evaluating ground contact for the Tackler ...... 169

xv Table 7.1: Number of fields and completion rate for the tackles analysed...... 176 Table 7.2: Fields with ‘unsure’ or ‘unknown’ ...... 178 Table 7.3: Cross tabulation of the raw count for tackle complete against what happened if the tackle was not complete demonstrating the internal consistency between the fields ...... 179 Table 7.4: Cross tabulation of the raw count for tackle complete against ground contact coding demonstrating the internal validity between the fields...... 180 Table 7.5: Player grouping of the Ball-carrier and Tackler as a proportion of all tackles ...... 181 Table 7.6: Tackle type as a proportion of player position grouping (rows add to 100%) ...... 182 Table 7.7: Number of tackles by subjectively assessed impact force and tackle type ...... 182 Table 7.8: Relative height by relative mass of the Ball-carrier to the Tackler as a proportion of all tackles...... 183 Table 7.9: A presentation of tackle type by ground and weather conditions ...... 188

xvi TABLE OF FIGURES

Figure 0.1: The names of the playing positions in rugby union, indicating the location on the field at a scrum (from International Rugby Board, 2008)...... xxiii Figure 0.2: The rugby union playing field (from International Rugby Board, 2008)...... xxiv Figure 1.1: An outline of the research process described in this thesis ...... 8 Figure 2.1: The sequence of injury prevention (van Mechelen, et al., 1992) ...... 11 Figure 2.2: Haddon’s Matrix for identifying contributors to injury in motor vehicle accidents (Haddon, 1999) ...... 15 Figure 2.3: The multi-factorial model for athletic injury (Meeuwisse, 1994) ...... 16 Figure 2.4: A comprehensive theoretical model of injury in Australian rules football (Norton, et al., 2001) ...... 17 Figure 2.5: McIntosh’s injury model (McIntosh, 2005a) ...... 18 Figure 2.6: Bahr & Krosshaug’s (2005) comprehensive model for injury causation...... 19 Figure 2.7: A dynamic, recursive model of aetiology in sport injury (Meeuwisse, et al., 2007)...... 19 Figure 3.1: A comparison of the proportion of tackles and ball contest events recorded in six levels of play...... 24 Figure 3.2: Direction of the tackle (Wilson, et al., 1999) ...... 59 Figure 3.3: Position of all injuries recorded in Garraway et al. (1999; n=72) superimposed on the field of play...... 65 Figure 3.4: Criteria for qualitative analysis from a scientific perspective (Patton, 2002; p 544) ...... 80 Figure 3.5: Integrated model of qualitative analysis (Knudson and Morrison, 2002) ...... 81 Figure 3.6: A strategy for the subjective analysis and observation of human movement (Arend & Higgins, 1976) ...... 83 Figure 3.7: The deterministic or hierarchical analysis model (Hay & Reid, 1988) ...... 85 Figure 3.8: An approach to qualitative movement analysis for performance intervention (modified from McPherson (1996)) ..... 86 Figure 3.9: Fields included in video analysis of the tackle by McIntosh, et al. (2005) ...... 88 Figure 3.10: An analysis of tackling (Wilson, et al., 1999) ...... 90 Figure 3.11: Fields included in Football incident analysis (FIA), Andersen et al. (2003) ...... 93 Figure 3.12: Fields included in video analysis of handball injuries by Oehlert, et al. (2004) ...... 95

xvii Figure 3.13: Video analysis fields used to evaluate blows to the head and face in Taekwondo (Koh & Watkinson, 2002) ...... 97 Figure 4.1: An outline of the process used to develop the tackle analysis protocol...... 112 Figure 4.2: An analysis of factors resulting in an injury outcome arising from the tackle skill based on a model presented by Bahr and Krosshaug (2005) ...... 123 Figure 4.3: A hierarchical analysis of tackling from the perspective of the Tackler, based on the method of Hay & Reid (1988) ...... 125 Figure 4.4: An outline of the coding process ...... 127 Figure 4.5: Fields in the tackle analysis protocol ...... 130 Figure 5.1: An overview of the number of fields and mean agreement rate for each level of the analysis ...... 142 Figure 6.1: Plot of agreement in IRR1 compared to IRR2 ...... 159 Figure 6.2: An overview of the number of fields in the analysis and the mean agreement rate for the analysis levels ...... 161 Figure 7.1: Number of tackles by field position ...... 187

xviii LIST OF TERMINOLOGY

Rugby specific terminology1

Tackle: An attempt by an opponent to stop the Ball-carrier Ball-carrier: A player in possession of the ball Tackler: Any opponent who attempts to hinder the Ball-carrier Ball contest event: A match event where possession for the ball is contested by members of opposing teams, such as a ruck or maul etc. Scrum: A restart event occurring after a stoppage or minor infringement of the rules. Eight players from each side are arranged in three rows (see Figure 0.1, positions 1 to 8) and, binding onto each other, interlock with the opposing team to push against each other for possession of the ball Ruck: A ball contest event where the ball is on the ground that involves one or more players from each team who are on their feet and in contact with one another. A ruck may occur after a tackle Maul: A ball contest event that occurs when the supporting team mates bind to the Ball-carrier, who is held by one or more opponents. All players must be on their feet. A maul may occur after a tackle. Lineout: A restart event used when the ball has left the field of play where the ball is thrown in by one player, between a formation of two lines of players from opposing teams arranged perpendicular to the sideline. Player position: The playing role of an individual in the team Field position: The location (of a match event) on the field

1 All definitions from the laws of the game of rugby union International Rugby Board. (2010). The laws of the game of rugby union 2010. Dublin: IRB. except the definition for the tackle, from Oxford English Dictionary (“Tackle”, OED, 2005) and playing position and field position xix Tackle analysis protocol

Fields: The critical feature or trait to be analysed in the protocol Field variables: The descriptors (often categorical) used to evaluate a trait within a field Dichotomous rating: Field assessed as a choice between two options (Yes/No, Present/absent etc.) Ordered categorical rating: Fields assessed by variables that are ordered but provide no quantitative description of scale (low, medium, high, etc.) Nominal rating: Field assessed by variables that have no quantitative ordering (shoulder, smother, jersey tackle etc.) Rater or coder: A user applying an analysis protocol to a movement Aetiology: The cause, causes or manner of causation of a disease or condition (“Aetiology”, Oxford English Dictionary, 2011) Cause: a person or thing that gives rise to an action, phenomenon, or condition. Something that produces an effect (“Cause” Oxford English Dictionary, 2011) Technique analysis: Analysing movement and evaluating performance (Lees, 2002)

xx LIST OF ABBREVIATIONS

ARU Australian Rugby Union

FIA Football Incident Analysis

IRB International Rugby Board

NSWRU New South Wales Rugby Union

NZRU New Zealand Rugby Union

RFU Rugby Football Union, England

RUISS Rugby Union Injury Surveillance Study

UNSW the University of New South Wales

xxi AN INTRODUCTION TO RUGBY UNION

Rugby union football (or rugby union, or rugby) is a contact invasion game played between two teams of fifteen players. The objective of rugby union is to score more points than your opponents by retaining possession of the ball and passing it between team members to move into opposition territory. The maximum number of points (five) is awarded when the ball is grounded in the opponent’s in-goal to score a “try”. Additional points are scored by kicking the ball between the opposition goal posts. Attempts at goal may be made during play (three points, known as field goals), or may be awarded following infringements (three points, known as penalties) or the scoring of a try (two points, known as conversions). Opponents attempt to prevent the progress of the team with the ball and create contests to win possession for their team. The tackle is the skill used to achieve these two important tasks in rugby, halting the Ball-carriers progress and creating an opportunity to obtain possession, making it a crucial skill for on field success.

Teams are comprised of two player position groupings, the forwards and the backs (Figure 0.1). Each grouping specialises in specific skills and their anthropometric profiles reflect this. The forwards are generally heavier and taller and are involved in winning possession of the ball in scrums, line-outs and rucks where their size is an advantage. Backs are generally leaner, more agile and aerobically fit than forwards (Duthie, Pyne, & Hooper, 2003a). The role of the backs is to run and pass the ball to score points.

xxii Figure removed due to copyright restrictions

Figure 0.1: The names of the playing positions in rugby union, indicating the location on the field at a scrum (from International Rugby Board, 2008).

Rugby is played mainly during winter on a natural grass playing field measuring 100 metres by 70 metres (Figure 0.2). The duration of a match varies from 40 to 80 minutes depending on player age and grade. Matches are widely played by participants of all ages at the community level. In 2004 there were more than three million registered players worldwide of both genders, making it the second most popular football code after soccer (International Rugby Board, 2004). The Rugby World Cup is the third largest international sporting event behind the Summer Olympics and FIFA World Cup. The 2007 Rugby World Cup had an estimated global television audience of over four billion viewers (International Rugby Board, 2007).

xxiii Figure removed due to copyright restrictions

Figure 0.2: The rugby union playing field (from International Rugby Board, 2008).

Rugby union football is described in the playing charter of the IRB as a physically challenging sport allowing players of all shapes, sizes and abilities to participate. It is a sport which is distinguished by collisions occurring between players during contests for the ball (International Rugby Board, 2005c). As a collision sport, body contact between opponents is symbolic of the challenging nature identified in the playing charter. It is this aspect of physical competition which is credited by proponents to develop courage, determination, sportsmanship and teamwork. However, contact sports have a higher risk of injury than non-contact sports. Collisions between players on the rugby field may expose players to loads above that which the body structures can tolerate, in addition to those sustained during normal sporting activities, such as running and jumping. As a result, rugby union possesses an inherent injury risk.

xxiv xxv

CHAPTER ONE

INTRODUCTION AND STATEMENT OF THE

PROBLEM

The positive benefits to health that are obtained from participation in sport can be offset by the risk of sustaining a sporting injury (Junge, Cheung, Edwards, & Dvorak, 2004; van Mechelen, Hlobil, & Kemper, 1992). Sporting injuries are amongst the most common causes of emergency department presentations in Australia for both adults and children, and their direct and indirect costs in comparable societies are high (Cumps, Verhagen, Annemans, & Meeusen, 2008; Finch, Boufous, & Dennis, 2007). Sporting injuries can require lengthy rehabilitation that not only prevents the injured athlete from participating in their sport, but also affects the individual’s ability to fulfil their duties in the workplace. As a result, sporting injuries detract from participation in sport and physical activity leisure activities and their prevention is an important method of increasing the exposure to the healthy benefits of sport. It is from the perspective of injury prevention that this research was initially formulated.

Van Mechelen et al. (1992) defined priorities for sports injury prevention according to incidence and severity. Injury surveillance research in rugby union confirms that it has a similar injury incidence to other collision sports such as rugby league and Australian rules football (Gabbett, 2004; Orchard & Seward, 2002). Within rugby, the tackle, a collision event between two players, has been consistently identified as possessing a higher injury incidence rate than other phases of play or match events. Tackle injuries also possess high injury severity, and have been consistently highlighted as a topic for injury prevention research (Bird et al., 1998; Garraway & Macleod, 1995; Inglis & Stewart, 1981; Lee & Garraway, 1996; McIntosh & Savage, 2005; McManus & Cross, 2004; Wilson, Quarrie, Milburn, & Chalmers, 1999). Before successful interventions to reduce injury incidence can be

1 implemented, the aetiology of an injury must be explicitly understood (Bahr & Krosshaug, 2005; Meeuwisse, 1994). At the time this research was undertaken, little was known about the tackle or appropriate methods for analysis.

Three frameworks provide the basis for analysing human movement: quantitative analysis, qualitative analysis and predictive analysis. Quantitative analysis obtains numerical measures through objective methods (Hall, 2006). Qualitative analysis is subjective evaluation of a specified target (Marshall & Elliott, 1995). A qualitative analysis can also be objective, not through obtaining a numerical measurement to describe movement but in terms of evaluating a target or phenomena with consistent results (Sofaer, 1999). It is most valid and reliable when it is systematic and based on scientific principles (Patton, 2002). Predictive analysis estimates the outcomes of movements through known inputs (Lees, 2002). Each system has its advantages and disadvantages and generally a thorough understanding of a subject is the result of successful utilisation of all three methodologies.

1.1 What is a Tackle?

The tackle is an important contact event in rugby union between a Ball-carrier and at least one Tackler. The aim is dependent upon the perspective of the player involved. The Tackler must attempt to prevent the Ball-carrier from gaining territory and to win possession of the ball for their team. The Ball-carrier must endeavour to minimise the impact of the Tackler or avoid the contact with the Tackler completely (ARU, 2006a). The tackle is defined in the laws of rugby union in Law 15 as occurring when the Ball-carrier is held by an opponent (the Tackler) and brought to ground (International Rugby Board, 2005b).

Situations where one or both the Ball-carrier and Tackler do not go to ground or where contact is broken or evaded completely are not tackles according to this law. The law provides an outcome (the Ball-carrier is held and the Ball-carrier and Tackler fall to the ground) but it does not specifically address the purpose of a tackle (to hinder physically the progress of the Ball-carrier). In the context of the

2 rules, the purpose of Law 15 is to serve as a reference for the identification of the phases of play immediately following contact or collision between players, such as rucks, when a Ball-carrier and Tackler go to ground, and mauls, when players remain on their feet, and what players can and cannot do in these situations.

Law 15 – The Tackle (International Rugby Board, 2005b)

A tackle occurs when the ball-carrier is held by one or more opponents and is brought to ground. A ball-carrier who is not held is not a tackled player and a tackle has not taken place. Opposition players who hold the ball-carrier and bring that player to ground, and who also go to ground, are known as Tacklers. Opposition players who hold the ball-carrier and do not go to ground are not Tacklers.

An alternate definition of the tackle is provided in the OED (“Tackle”, 2005):

5. (a) In Rugby, to seize and stop (an opponent) when in possession of the ball.

The OED definition and Law 15 are similar in that both reference physical contact (held and seize) between players. On the other hand, the OED definition retains focus on stopping and holding the Ball-carrier but does not limit the event to one in which ground contact is made by both players.

As will be presented later in this thesis, the tackle presents the highest risk of injury in rugby union, having a higher injury incidence than other match events such as the scrum, ruck, maul and line out. Nevertheless, methods of ameliorating injury risk within the tackle are restricted. As several authors note, rugby is a contact sport and collisions are an important part of the game. Sanctions against tackles that present an obvious risk of injury, such as tackles above the line of the shoulders and tackles without the use of arms (shoulder charges) have been imposed. However, changes to the rules to eliminate high velocity tackles, or tackling completely, would lead to a drastic change in the nature of rugby union (D. C. Hughes & Fricker, 1994).

3 Tackles are complex and multi-factorial collision events and injury may be associated with the presence of any one particular factor or skill aspect, or the interaction of multiple factors. Complex skills are not readily described in quantitative terms, whether attempting to analyse the flow of the game, scoring opportunities, player to-player interactions or injury situations (Andersen, Larsen, Tenga, Engebretsen, & Bahr, 2003). Because of the number of potential contributing causes and limitations of method, aetiology cannot be evaluated in the laboratory.

An alternative method of analysis is to examine tackles retrospectively from match video using a qualitative analysis protocol. Such an analysis could be used to establish not only the characteristics of tackles where an injury occurs, but also to inform the representative characteristics of tackling technique in rugby. Representative data would provide feedback for coaches on skill execution with regard to coaching guidelines and allow for comparison with the characteristics of tackles where an injury occurred. Specific aspects of tackling technique, which require focused research, could be isolated and suitable methods developed for quantitative testing.

A comprehensive analysis protocol, which takes into account event, match and environmental factors, describes potential injury situations and which could be applied to match video, did not exist at the time this research commenced.

1.2 Research Objectives

The main objective of this research was to develop an analysis protocol that could be applied to match video to analyse tackling technique. A thorough analysis of the tackle skill is essential to describe the representative tackling technique and skills that are employed by rugby players. The description of the tackle event produced during analysis with the protocol must be comprehensive, valid and reliable.

4 To be effective, the protocol must consider and be able to effectively describe:

x The tackling skills employed by players (e.g. the type of tackle, body positioning etc.) x The patterns of injury in the tackle (e.g. body regions affected, specific loading mechanisms) x Biomechanical parameters of skill performance (e.g. momentum, player movement direction, dynamic stability etc.) x Extrinsic factors such as match and environmental conditions

1.3 Research Questions

Three questions were posed for this research:

1. What aspects of skill should be included in a qualitative analysis protocol?

2. Which observable aspects of tackle technique may be used to describe injury situations?

The third question has two parts:

3. Can a reliable qualitative analysis protocol be developed to analyse the tackle in rugby union?

a. Can reliable estimations of biomechanical parameters be made from video using qualitative analysis techniques?

b. Can reliable estimations of tackle skill factors be made from video using qualitative analysis techniques?

5 1.4 Research Hypothesis

A reliable qualitative protocol can be developed to analyse the tackle in rugby union through critical features of technique and biomechanical parameters.

1.5 Research Outcomes

Analyses produced with the protocol should contribute to our knowledge of in situ execution of the skill, including identifying factors which may be related to injury identifying changes in technique and injury patterns over time. These results can then be used to develop further research examining the tackle and injury aetiology. When used in combination with prospective injury surveillance data, the protocol could be used to monitor the effectiveness of skills training programs for injury prevention and provide evidenced based support for revisions to coaching and injury prevention interventions. A simplified version of the protocol may also be developed for coaches to monitor skill execution and progression amongst their athletes.

1.6 Thesis Structure

The thesis describes the process of developing and testing the analysis protocol as a series of staged activities. The structure of the thesis is as follows:

x Introduction x Literature review x Development of the analysis protocol x Reliability testing of the analysis protocol x Reliability testing of the revised analysis protocol x Discussion and conclusions

6 The research process is outlined in Figure 1.1. The review of literature commences with the presentation of sports injury prevention frameworks from which the necessity for investigating the tackle and the tackle analysis protocol originated (Chapter Two). A review of literature is presented in Chapter Three. Tackle injuries are reviewed in the broader context of rugby injuries before focussing specifically on research and the trends of injury in the tackle. The methods for analysing sporting skills from performance and biomechanical perspectives will then be reviewed. The literature review was conducted at the commencement of the research to inform the development of the analysis protocol and was repeated in 2011 to collect additional references for the discussion. The development and reliability testing of the protocol consisted of three staged activities conducted over a two-year period. The methods and results of these processes are presented independently of each other in three separate chapters. Chapter Four elaborates upon the methods that were used to develop the tackle analysis protocol and describes the process that was followed to indentify critical features of technique, injury risk factors and other attributes that were used to construct the analysis fields and create field variables. Chapter Five presents the methods and results of formal inter-rater reliability (IRR) testing of the protocol amongst raters and describes the process that resulted in a number of revisions that were made to improve reliability. Chapter Six describes the methods and results of a second IRR study that was conducted 12 months after the first IRR study to assess the efficacy of the changes. The results from an analysis of 100 tackles with the protocol are presented in Chapter Seven to demonstrate its application. The results of the three stages of development and reliability testing of the protocol will be discussed in Chapter Eight.

7 Systematic First Second development reliability reliability Final of the analysis study study Protocol protocol

Review existing 2nd draft Final Optimisation methods coder definitions of delivery/ manual document analysis with the protocol Collection of information about skill execution and Inter rater Inter rater injury reliability reliability testing testing Arrangement of information

Application of the protocol to 1st draft coder Review of Evaluation of a sample of manual results in results expert panel 100 tackles

Presentation of protocol to expert panel

Combination of protocol with RFU analysis protocol

Figure 1.1: An outline of the research process described in this thesis

8 CHAPTER TWO

INVESTIGATING THE TACKLE USING A SPORTS

INJURY PREVENTION FRAMEWORK

The notion that prevention is better than cure is one that is commonly repeated. It is likely that this sentiment has been around for many years, but it was first attributed to Henry de Brocton, a jurist who lived in Britain during the 13th century. In his work De Legibus et Consuetudinibus Angliae he wrote:

“it is better and more useful to meet a problem in time than to seek a remedy after the damage is done.”

The saying has also been attributed to the 15th century scholar Desiderius Erasmus. Regardless, the notion is an old one, and the phrase has become cliché. Thus, it is somewhat surprising that sports injury prevention is a relatively new discipline of the human movement sciences. A recent analysis of literature revealed over 5,270 original research articles in sports injury prevention were published between 1938 and 2009, and approximately half of these were published after 1995 (Klügl et al., 2010). “Sport” “injury” emergence has coincided with two notable events: the emergence of sport as entertainment and increases in participation rates. Sport has become increasingly professional and commercialised, particularly at the elite level, and it is clear that the most effective way of capitalising on sport as entertainment is to maximise on field success and acceptability of the sport. In Australia, on field success generally results in increased match attendance and media coverage and is related to the fitness and uninterrupted availability of the most skilled players. There are potentially many factors which affect reach, however within the sphere of injury prevention, parental concern has been identified as a barrier to youth participation (Boufous, Finch, & Bauman, 2004). Many sporting bodies acknowledge a duty of care to participants and demonstrating safety may be an effective way to increase acceptability and participation.

9 Secondly, participation rates in organised sport and informal physical activity have increased in many countries including Australia, where between 1997 and 2010 there was an increase of 80% to 11 million people who had participated in sport at least once in the preceding 12 months (Australian Bureau of Statistics, 1998, 2010). One possible explanation for this may be the emergence of campaigns recommending physical activity itself as a preventative measure to reduce lifestyle illnesses such as cardio-vascular disease, metabolic syndrome and some forms of cancer (Bauman, 2004; Shephard, 1995; van Mechelen, et al., 1992). This has been recognised with the introduction of physical activity guidelines in many countries and sponsored programs encouraging participation in regular physical activity such as ‘Life be in it’ and ‘10,000 steps’ in Australia, ‘IN FORM’ in Germany and ‘Let’s get moving’ in the United Kingdom.

However, sports participation can also result in injury which may lead to significant physical, psychological and financial effects due to ongoing treatment and rehabilitation and an increased load on the public health system (Cumps, et al., 2008; Finch, Valuri, & Ozanne-Smith, 1998; Junge, 2000). As outlined in the introduction, tackle in rugby has been identified by prospective injury surveillance studies as an important target for injury prevention research and it was from this perspective that evaluation of potential methods of analysis originated. The purpose of this chapter is to provide context for the origins of this research by presenting the sequence of sports injury prevention and cognitive frameworks for assessing risk factors and determining aetiology.

2.1 The Sequence of Sports Injury Prevention

The sequence of sports injury prevention (Figure 2.1) is a processual model presented by van Mechelen, Hlobil and Kemper (1992) to assess and ameliorate injury risks in sport. The sequence commences with injury surveillance to identify and describe the extent of injury problems. The extent of the injury problem must be described in terms of the body regions injured, the frequency of occurrence

10 (injury incidence) and the duration of recovery (injury severity). After the extent of an injury problem has been established, it should be investigated so that the causes can be identified with the aim of controlling the injury situation and ameliorating risk through targeted preventative interventions (Haddon, 1999; Krosshaug, Andersen, Olsen, Myklebust, & Bahr, 2005). The cyclical sequence then returns to monitoring to evaluate the effectiveness of interventions and emergence of further injury problems.

1. Establishing the 2. Establishing extent of the sports aetiology and injury problem mechanism of injuries Figure removed due to copyright restrictions

4. Assessing the 3. Preventative effectiveness of interventions to interventions by reduce injury repeating step one incidence/severity

Figure 2.1: The sequence of injury prevention (van Mechelen, et al., 1992)

There are two precedents in rugby union research that adhere to the sequence of van Mechelen and colleagues. In the 1970’s and 1980’s, for example, several authors noted high rates of preventable dental injury in rugby union (Chapman, 1985; R. M. Davies, Bradley, D., Hale, R. W., Laired, W. R., and Thomas, P. D., 1977; Upson, 1982). As a result, the use of mouthguards to prevent dental injury is now compelled in youth and encouraged in all other players in Australia. In New Zealand, compulsory mouthguard use coincided with a 43% reduction in rugby dental injuries between 1995 and 2003 (Quarrie, Gianotti, Chalmers, & Hopkins, 2005). Similarly, in the scrum, research described observations for the occurrence and circumstance of catastrophic spinal injury (Burry & Gowland,

11 1981; Scher, 1977; Sovio, van Peteghem, & Schweigel, 1984). As a result of subsequent biomechanical research, changes to the laws of scrum engagement were implemented to prevent catastrophic spinal injury (Milburn, 1990). In the case of both the scrum and dental injuries, an injury problem was identified through observations of treating physicians or trainers, confirmed with results obtained through research. Interventions to address the risk were then introduced and the efficacy of the interventions were monitored through continued surveillance. For dental injuries the intervention appears to have been successful, while for the scrum the evidence is inconclusive (Bohu et al., 2009; Carmody, Taylor, Parker, Coolican, & Cumming, 2005; Quarrie, Gianotti, Hopkins, & Hume, 2007).

The results of injury surveillance research have consistently identified that injuries occur more frequently in the tackle than in other match events at all levels of play, identifying the tackle as an important target for sports injury prevention research. (Bathgate, Best, Craig, & Jamieson, 2002; Brooks, Fuller, Kemp, & Reddin, 2005a; Durie & Munroe, 2000; McIntosh, Savage, & Dutfield, 2008; Nathan, Goedeke, & Noakes, 1983). The second step of the sequence of injury prevention is to establish causes of injury. Describing injury aetiology requires a thorough understanding of the injury situation and evaluation of risk factors through careful investigation of the circumstances surrounding injury occurrence (Bahr & Krosshaug, 2005; Haddon, 1999). The complexity of the tackle makes identification and evaluation of risk factors and injury aetiology difficult. Tackles may occur at high speed, result in large impact forces and involve several players, with each player possessing differing intrinsic attributes that may predispose them to injury. Injury may be associated with the tackle impact or whilst the player is held and falling to the ground following a tackle. Additional environmental factors such as weather and ground hardness, and match factors such as the match score, team mates in support and field position could all conceivably influence the outcome of a tackle event and subsequent injury occurrence. While any of these are independent injury risk factors in their own right, injury may not be the result of any one particular factor but is probably associated with a confluence of multiple factors (Meeuwisse, 1994). Understanding aetiology can allow for management of

12 risk factors to gain control of the situation in which the injury occurs (Haddon, 1999). Interventions such as personal protective equipment and alterations to the rules are an obvious and widely utilised method to ameliorate injury risk (Krosshaug, et al., 2005) and have previously been used to address rugby injury problems. Methods for investigating injury risk factors will be discussed in section 2.2.

At the commencement of this research, the aetiology of tackle injury was not clear. The identified aim of the tackle analysis protocol was to develop a qualitative analysis protocol that could be applied to match video to analyse tackling technique. Through potential outcomes of clarifying injury causation in the tackle and identifying foci for further research, the protocol may be utilised as a tool to develop interventions to ameliorate injury risks in the tackle, as per the third step of van Mechelen and colleague’s injury paradigm. The analysis protocol may also form an integral part of monitoring changes in skill patterns and the effectiveness of these interventions (step 4 of the paradigm). As McIntosh (2005a) describes, there is ambiguity that managing one injury risk may result in risk compensation and no change to the incidence rate, or even an increase. (Hagel & Meeuwisse, 2004; McIntosh, 2005a). Therefore, interventions require support from ongoing monitoring programmes to evaluate risk compensation, changes in risk factors and to inform evolution of preventative interventions that have met their objectives to maintain their efficacy. For the tackle analysis protocol to contribute to this process, it is essential that it is capable of describing tackling skills and injury situations. The remainder of this chapter will review existing methods of determining the cause of sports injury.

13 2.2 Establishing the Cause of Injury

According to the sequence of injury prevention, once events presenting the highest risk of sports injury have been identified, the cause, or causes, of injury must be isolated and described. In 1992, van Mechelen, Hlobil and Kemper wrote that the knowledge of risk factors relevant to sporting injury in all sports was limited. In rugby union this view still had merit when the tackle analysis protocol was developed. Some research questioned the effectiveness of rules that have been introduced to ameliorate risk factors for injury in the scrum, while in the tackle, two studies utilising the protocol that will be described have recently proposed risk factors for injury and require confirmation from further research (Fuller et al., 2010; McIntosh, Savage, McCrory, Fréchède, & Wolfe, 2010; Quarrie, et al., 2007).

To understand injury causation, injury should be described in aetiological terms and not simply identifying the event that it was associated with (Bahr & Krosshaug, 2005). Haddon attended to this concept in 1968 from the perspective of traffic accident prevention. He observed that control of pathological illness was attained through understanding the agent of cause and that epidemiology should follow a similar ideology. As an example, he noted that the term ‘accident’, used to describe an event from which a traffic injury arose, was representative of a simplistic belief that ‘accidents’ were random, serendipitous events that could not be controlled (Meeuwisse, 1994). He argued that ‘accidents’ are caused through a failure to perceive and failure to react to a risk and that once the event is understood in aetiological terms, preventive measures can be introduced and the event can no longer be considered as an accident. Sports injuries too, may be caused by a failure to perceive the risk associated with an event or to react to a situation in an appropriate manner because of poor preparation (Bahr & Krosshaug, 2005). A number of models or investigative frameworks have been presented to assist in evaluating or describing aetiology through the identification of risk factors associated with injury.

14 Haddon (1999) used a matrix to arrange information according to arbitrary temporal phases, usually pre-event, during the event and post event (Figure 2.2). Potential risk factors and other useful information are recorded according to the perspective of ‘components’ of the event, or targets such as agonists (e.g. Tackler, in the context of a tackle event), antagonists (e.g. Ball-carrier) or other participants (e.g. spectator, referee etc.). Additional matrices may list measures that could be applied to mitigate risk factors. Some subjective judgement and knowledge of the event is still required to identify variables and injury risk factors. One limitation of Haddon’s matrix is determining the interaction between the aspects. While individual aspects are easily listed in such a matrix, this may not be the best method to assist with evaluation of relationships between a number of potential risk factors. Because the agent of cause for sports injury has been proposed as multi- factorial this is an important consideration (Meeuwisse, 1994; van Mechelen, et al., 1992).

Participant/resource

Figure removed due to copyright restrictions

Figure 2.2: Haddon’s Matrix for identifying contributors to injury in motor vehicle accidents (Haddon, 1999)

15 Meeuwisse (1994) presented a similar method to Haddon that allows for the risk factors to be listed but which may also assist in understanding the interaction between a number of independent risk factors. Meeuwisse’s framework (Figure 2.3) describes injury in terms of:

x intrinsic factors predispose an athlete to injury x extrinsic factors make a predisposed athlete susceptible to injury x and an inciting event a specific set of circumstances which exacerbate injury risk

Figure removed due to copyright restrictions

Figure 2.3: The multi-factorial model for athletic injury (Meeuwisse, 1994)

Meeuwisse proposed that by utilising the framework to complete an analysis for all individuals affected by a particular injury, the common factors would emerge and relationships between various risk factors and injury would become clearer. A drawback of both methods discussed so far is that they do not provide any guidance on how to evaluate risk factors or the inciting event.

Norton, Schwerdt, & Lange (2001) presented a theoretical model of injury as a result of research into lower limb injuries in Australian rules football (Figure 2.4). Their model highlights a number of risk factors that the authors have identified as important contributing factors for injury, such as game speed and ground

16 characteristics. The authors identify a number of factors that influence game speed, including rules, demands of the media and supporters (i.e. beliefs in how the game should be played), the level of competition, in addition to the physical demands on the players through, for example, workload and positional demands. The second major risk factor, ground characteristics, was a contributing factor to game speed, and these two dependent factors influenced the type and magnitude of the collisions experienced during a game. The model by Norton and colleagues differed from earlier models in that it was the first model to attempt to evaluate the contributing factors of injury in a ‘tackle’ situation/event, specifically focussing on variables which may moderate mechanical loading.

Figure removed due to copyright restrictions

Figure 2.4: A comprehensive theoretical model of injury in Australian rules football (Norton, et al., 2001)

McIntosh (2005a) developed on the mechanical loading experienced by players. The model includes aspects that could be described under intrinsic variables of Meuwisse (1994) and the mechanism of injury may reflect both the inciting event and extrinsic factors. While the model was presented from a more generic perspective that was not exclusive to an impact between players, it requires the inciting event to be described in terms of the mechanical load experienced by the player. As a result, the model describes injury from a largely biomechanical

17 perspective but it also incorporates behavioural aspects that may modulate injury outcome such as coaching, training programs undertaken and skill level (Figure 2.5). McIntosh’s model also accounts for exposure to near misses events that did not cause injury, which he proposed may result in risk compensation behaviour.

Figure removed due to copyright restrictions

Figure 2.5: McIntosh’s injury model (McIntosh, 2005a)

Following McIntosh’s model, the importance of describing the inciting event was further addressed by Bahr and Krosshaug (2005). They developed on Meeuwisse’s model, proposing that a full description of the inciting event should include information from several perspectives. The authors presented several criteria for describing the inciting event that incorporated gross and detailed biomechanical descriptions of the event, as proposed by McIntosh, as well as sport specific characteristics (Figure 2.5). The authors also identified the importance of developing standards for the description of injury events in specific sports, such as the protocol that has been developed in this research.

18 Figure removed due to copyright restrictions

Figure 2.6: Bahr & Krosshaug’s (2005) comprehensive model for injury causation.

Finally, Meeuwisse, Tyreman, Hagel and Emery (2007) further revised Meuwisse’s earlier multi-factorial model for athletic injury (Figure 2.3) to address the outcome of the injury and the consequences of repetitive participation. The authors incorporated the repetitive nature of sports activity, including events that lead to injury and those that do not lead to injury, in their model (Figure 2.7).

Figure removed due to copyright restrictions

Figure 2.7: A dynamic, recursive model of aetiology in sport injury (Meeuwisse, et al., 2007).

19

2.3 Summary

A complete understanding of injury causation needs to take into account the multi- factorial nature of sports injuries (Bahr & Krosshaug, 2005; Haddon, 1999; Meeuwisse, 1994; van Mechelen, et al., 1992). While the incidence and severity of injury in the tackle has been established, the presence of extrinsic factors, such as tackle type, the number of Tacklers, the direction of engagement, or the speed and momentum of the players prior to the impact at tackle injury events has not been evaluated. Any number of these factors listed may influence injury risk either independently, or in combination with one another. Investigating the tackle from a sports injury prevention framework will assist in identifying risk factors for injury for the players involved and may assist in isolating relationships between risk factors, but an effective tool is required.

20 CHAPTER THREE

REVIEW OF LITERATURE

3.1 Methods for literature review

The Medline and SPORTDiscus databases were used to source literature for this review. A list of the search terms used to identify literature relevant to the topic of skill analysis and the tackle in rugby union is provided in Table 3.1. To conduct a broad search and identify all occurrences of the search term within the fields of the citation, all searches were performed using ‘keywords’. The literature search was first performed in March 2006 to inform the development of the tackle analysis protocol. In June 2011 the search was repeated to incorporate current research for the discussion.

The results incorporated papers published between 1975 and 2010. Searches were conducted to identify research in rugby union and the tackle. All of the articles found during searches for the keyword “rugby” were in English and no conditions were selected to exclude articles other than periodical publications from searches with SPORTDiscus. Many results from the keyword search were irrelevant to the area of interest and each citation returned during the search was individually reviewed. This intensive method was used when other methods failed to identify the body of research expected, i.e. when too few citations were returned the search was expanded and each citation reviewed. The search results were saved in separate Endnote TM libraries for review and management.

A literature search was also performed to identify research methods evaluating human movement from sporting, clinical and industrial applications. Excluding the articles that were duplicated through the search (Table 3.1), the initial search (in 2006) yielded 358 articles. It was necessary to perform additional search to identify content for qualitative analysis, and this will be described in section 3.5.6. After an

21 initial review of abstracts, 138 articles were selected for the literature review because the described the results of injury surveillance in rugby union, assessment of injury from video in other sports or presented theoretical models evaluating injury aetiology. The reference lists of these articles were then scrutinised to identify other relevant material which were not identified during the initial search. An additional 34 articles were located during this process. Twenty three books or book sections were consulted to provide specific additional information. The main contributions for the literature review were drawn from injury prevention and coaching literature.

Search Term Medline SPORTDiscus Rugby Union & Injury 165 406† or Injuries Rugby Union & Tackle 31 61

Tackle and Injury 142 140† Qualitative analysis; or* 4437 (Review Articles) (239) Technique Analysis; or* 182 7 Qualitative - Biomechanical Analysis* Sports Injury 46 - Prevention Skill Analysis 12 73

Table 3.1: Search terms used to identify literature for this review. †Articles from serial publications were excluded * Search terms were combined in SPORTDiscus

22 3.2 Frequency of Match Events

A limited number of studies have evaluated the frequency of match events in field or invasion sports. Although similar information is often supplied to observers during sports broadcasts in Australia, at the time that this research commenced only four studies had been conducted, one in Australian rules football (Appleby & Dawson, 2002) and three studies in rugby union. The three investigations of match event frequency in rugby union all enumerated match event frequency at different levels of play. Two studies evaluated events from adult rugby, either professional (Fuller, Brooks, Cancea, Hall, & Kemp, 2007) or elite (Quarrie & Hopkins, 2007) and one study evaluated events from youth rugby (McIntosh, Savage, & Nicholson, 2005). All three studies were conducted in different geographical regions (Australia, New Zealand, and the United Kingdom) but investigated match events from matches that were played over a similar period (2003 to 2005). The latter aspect minimises the influence of changing styles of play and law variations. A comparison of the proportion of these events per match is presented in Figure 3.1. To produce this figure, the number of ball contest events from each study was pooled and divided by the number of games in the sample. When pooling the data supplied by Quarrie and Hopkins (2007), only the 2005 season was used to maintain consistency for the period analysed. The proportion of contests in a match by level of play was then calculated.

The combined results demonstrate that the tackle occurs more frequently than other match events such as the ruck, maul, scrum and line-out, accounting for approximately 50% of match contact events. The range of tackles observed per match was between 220 and 270 tackles at the professional and elite level (Fuller, Brooks, et al., 2007; McIntosh, Savage, et al., 2005; Quarrie & Hopkins, 2007). Ball contest events occurred less frequently, with the ruck accounting for between 31 and 34% of contact events, the line-out and scrum 5 to 6% and the maul 4% (Fuller, Brooks, et al., 2007; Quarrie & Hopkins, 2007). This observation emphasises the tackles importance in defence and creating a contest for possession.

23 Lineout

Scrum U13 U15 Opens Maul Colts Event Professional Elite Ruck

Tackle

0.0% 10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 70.0% Proportion of ball contest events

Figure 3.1: A comparison of the proportion of tackles and ball contest events recorded in six levels of play.2

From the comparison in Figure 3.1, there is a clear trend towards a decrease in the proportion of tackles in a match by level of play from youth to elite rugby. This coincides with increases in the number of rucks and line-outs and a decrease in the proportion of mauls. The proportion of scrums is relatively stable across all cohorts. More tackles and fewer rucks may indicate that a number of opportunities to create ball contests following a tackle are not realised. It may also be indicative of more effective tackles in terms of the Ball-carrier and Tackler going to ground in the higher levels of play. The latter hypothesis is supported by the decreased proportion of mauls in the upper age groups. This may mean that ground contact occurs more often for elite and professional players than in youth.

2 The proportion of events per match in elite rugby were calculated from data in Quarrie & Hopkins (2007) for the 2005 season. For professional rugby the proportion was calculated from Fuller et al. (2007) for the 2003/04 season and for youth rugby (U13 to colts) the proportion of match events was calculated from McIntosh, Savage & Nicholson (2005) as the average of the 2003 and 2004 seasons.

24 Some care needs to be taken in comparing results from different studies in this manner. Research methods which may influence the number of events identified in an analysis include the definition used to identify match events; the number of matches surveyed; and the quality of video used. The definitions used for identifying tackles and ball contest events were not provided in the research. Continuity amongst event definitions cannot be assumed. However, the authors stated that the analysts used in each study were familiar with rugby which should result in overlap in terms of the events identified. The effect of the definition may be further reduced by including a larger number of matches in the analysis to obtain results more representative of normal match patterns by presenting extremes in context of frequency. A result of this is that a larger number of more frequently occurring events are identified ideally from within the area of definition overlap between studies. The research of McIntosh, Savage et al. (2005) and Fuller at al. (2007) examined events from multiple games and seasons and should be more representative of the general tendency than Quarrie and Hopkins (2007), where the results from just one game were used.

3.3 Rugby Injuries

3.3.1 Considerations for the Comparison of Injury Data

There are a number of considerations when comparing rugby epidemiology studies which have largely used different methodologies to obtain data. The research has been conducted in different populations (age and level), different time periods (rule changes) and using different injury definitions, data collection methods and measures of exposure, making comparison between studies difficult. This issue has been common amongst sports injury epidemiology research and many sports, including cricket, football/soccer, and, recently, rugby union, have responded by developing a consensus statement for the conduct of injury surveillance studies (Fuller et al., 2006; Fuller et al., 2007; Orchard et al., 2005).

25 In addition to methodological differences, changes in match play (alterations to the dependence on kicking for territory or maintaining the ball in hand) can also affect a player’s exposure to injury risk. Patterns of match play vary between teams and level of play are prone to change over time with the influence of rule changes and changes in tactics (International Rugby Board, 2005a; Quarrie & Hopkins, 2007). For example, faster match speeds and increased ball in play time have led to increases in the number of tackles per game, while increases in player size could potentially result in more forceful collisions between players (McIntosh, 2005a).

Brooks and Fuller (2006) assigned the injury definitions used in rugby and other epidemiological research to three groupings:

1. Medical attention (all injuries requiring attention and which occur during participation are reported) 2. Lost time - missed session (an injury causes a player to leave the field and/or miss a subsequent training session and/or match) 3. Lost time - missed match (an injury causing a player to miss a subsequent match)

Injury data collected under a medical attention definition are observed to contain a higher proportion of minor physical impairment, such as bruising and abrasions, than injuries recorded under a lost time definition which contain a higher proportion of more serious and performance impairing injuries. Van Mechelen, Hlobil and Kemper (1992) stated that:

“Athletes cannot be fully fit unless they can take part in competition”

Unless researching the risk factors for a specific condition or nature of injury, it is the time lost definition which should be considered for the analysis of the tackle.

The injury definition used in a study has further implications when considering the injury statistics presented (e.g. proportion of injuries by Body region, injury nature or event). Research presenting the injury collected under a medical attention definition will also include these injuries in other injury statistics. This means that a large proportion of injuries identified as occurring during the tackle may be minor,

26 such as bruising and abrasions which may not have caused the player to cease their participation in the game.

3.3.2 Epidemiological Research in Rugby Union

As a result of the contact occurring between players and the frequency of contact events, rugby union has an inherent risk of injury (D. C. Hughes & Fricker, 1994). This has resulted in a number studies investigating injury patterns and a number of potential injury risks have been presented based on the findings. The methods used to described injury patterns in rugby union can be classified according to the epidemiological methods for sports science identified by Walter and Hart (1990):

x Case series examining specific injuries such as catastrophic spinal injuries x Case control x Comparative observational studies (Prospective injury surveillance studies including observations by referees etc.) x Randomised control trials

Case studies, or case series, present information about the occurrence of specific injuries. In rugby these have often been reported from the perspective of the treating physician. Case studies have generally been conducted in response to recognised injury problems to support law changes to make the sport safer. They are useful in the identification of common injury circumstances in a given sport and population and can assist in the identification of risk factors for an injury (Adams, 1977; Davidson, Kennedy, Kennedy, & Vanderfield, 1978; Scher, 1978, 1983a, 1991b; Silver & Gill, 1988). A number of studies have addressed the occurrence of catastrophic spinal injuries (Browne, 2006; Carmody, et al., 2005; O'Brien, 1996; Scher, 1983b; Silver & Gill, 1988; Williams & McKibbin, 1978), head injuries (McCrory, 1998) and facial injuries (Chapman, 1985; R. M. Davies, Bradley, D., Hale, R. W., Laired, W. R., and Thomas, P. D., 1977; Upson, 1982). However, case studies cannot provide information about how often injury is absent in similar situations (injury incidence) (van Mechelen, et al., 1992; Walter & Hart, 1990).

27 Prospective injury surveillance studies are useful in contextualising and evaluating the extent of an injury problem according to level and exposure of the athlete and monitoring changes in injury patterns (van Mechelen, et al., 1992). The earliest prospective injury surveillance study of rugby injuries was conducted in 1961 (Archibald, 1962). A number of prospective injury surveillance studies have been conducted in rugby union since then, at all levels of play from youth and community to state/provincial and international rugby. Recently the governing bodies of rugby in Australia, New Zealand and England have supported long term prospective injury surveillance studies (Bird, et al., 1998; Brooks, et al., 2005a; McIntosh, et al., 2008). The disadvantages of prospective injury surveillance studies are their time consuming nature, intensive commitments in personnel and data management, and resultant costs. As has been previously discussed in section 3.3, it has been difficult to compare the results from different studies owing to different data collection methodologies. The consensus statement on injury research in rugby may assist to resolve this issue (Fuller, et al., 2006).

Other studies to be conducted in rugby include case control studies (Garraway et al., 1999; Jones, Lyons, Evans, Newcombe, & Palmer, 2003), medical report and observations of match referees or treating physicians (Archibald, 1962; Davidson, et al., 1978). The results obtained from these studies using different methods must be interpreted cautiously to construct a broad overview of injury trends in rugby.

3.3.2.1 Injury Incidence

The injury incidence rate is a measure of the frequency of new injury events with respect to exposure (per person and unit of time; Kirkwood & Sterne, 2003). Whilst most studies have presented incidence rates per thousand player game hours, a number of injury definitions have been used to determine injury incidence, affecting the results as discussed in section 3.3. The type of injury definition and injury incidence rate recorded in studies using prospective data collection methods are summarised in Table 3.2 and, where possible, time loss incidence rates have

28 Injury Rate for all Missed game Authors Cohort definition* injuries injury rate McIntosh et al. 19.4 (2004) Schoolboy, Colts, McIntosh & 3 Open age, 27.8 Savage (2005) Professional McIntosh et al. and Elite 33.4 (2008) Hughes & 2 Open age 44.9 14† Fricker (1994) Garraway & 2 Open age 11.6 8.1† McLeod (1995) Garraway et 2 Open age 24.5 al.(2000) Clark et al. 2 Open age 16.6 (1990)

Targett (1998) 2 Professional 120 45.9†

Brooks et al. 2 Professional 91 40 (2005a) Bathgate et al. 2 Elite 69 (2002) Best et al. 2 Elite 97.9 (2005) Brooks et al. 2 Elite 218 58 (2005c) Durie and 2 Schoolboy 27.5 8.2 Munroe (2000) Junge et al. 1 Schoolboy 129.8 28.3 (2004)

Table 3.2: Type of injury definition, cohort and injury incidence rates (per 1000 player game hours) for injury surveillance studies in rugby union. * Injuries are grouped numerically according to definitions on page 26 † Injury incidence rate was calculated from information provided in the article.

29 also been presented to allow for effective inter-study comparison. The injury incidence rates presented in the studies reviewed were between 11.6 and 218 per 1000 player game hours for all injuries. The injury rates for lost time injuries were between 8.2 and 58 injuries per 1000 player game hours. Comparing the incidence rates for injury recorded by Targett et al. (1998) and Junge et al. (2004) according to inclusive and time loss definitions provides a clear demonstration of the effect of injury definition upon the rates collected. The wide variation may also reflect other reasons, e.g. differences in populations. For example, Garraway and McLeod’s study (1995) collected information at matches of amateur players, while Brooks’ study (2005c) recorded injuries arising from every session for an elite team in preparation for the 2003 Rugby World Cup.

3.3.2.2 Injury incidence and level of play

There is an increase in injury incidence associated with higher playing levels and grades (Table 3.2) (Bird, et al., 1998; Clark, et al., 1990; McIntosh, et al., 2004; McIntosh & Savage, 2005; McIntosh, et al., 2008). Possible explanations include:

x Longer match duration leading to increased exposure x Greater period of time with the ball in play resulting in more phases x Faster match speeds associated with increased skill levels x Stronger and heavier players

It is hypothesised that these produce matches with a higher frequency of more forceful collisions in tackles and ball contests, increasing the exposure of players to potential injury (Alsop, Morrison, Williams, Chalmers, & Simpson, 2005; Lee & Garraway, 2000; McIntosh, et al., 2008).

3.3.2.3 Injury Severity

Injury severity, a measure of the consequence of the injury to the individual or the seriousness of an injury, is used to describe the extent of an injury problem and is described by the duration of absence from rugby activities caused by an injury (van Mechelen, et al., 1992). Injury severity has been reported in two distinct ways in

30 the literature; either as the mean time lost per injury (i.e. the number of injuries divided by the sum of all weeks, days or sessions lost) or as a proportion of injuries according to the time taken to return to play e.g. mild 1-3 weeks, moderate 3-5 weeks, severe 5+ weeks.

Proportion of all injuries by severity Mean time Between one absent from Authors One week or Three weeks and three rugby less (%) or more (%) weeks (%) activity Best et al. 70 14 16 (2005) Bathgate et 64 14 22 al.(2002) Brooks et 14 days al.(2005c) Brooks et al. 54 26 20 18 days (2005a) McIntosh et al. 3 weeks (2004; 2008) Clark et al. 58.7 28.6 12.8 (1990) Hughes et al. 58.7 28.6 12.8 (1994)

Targett (1998) 71.4 18.4 10.2

Durie & 72 18.5 4.2 Munroe (2000) Junge et al. 52.1 36.6 11.3 (2004) McManus et 78 18 4 al.(2004)

Table 3.3: Injury severity in published injury surveillance research.

31 The injury severity reported for studies with comparable severity measures are presented in Table 3.3. There is a mean injury severity of between two and three weeks for rugby union injuries (Brooks, et al., 2005a, 2005c; McIntosh, et al., 2004; McIntosh & Savage, 2005; McIntosh, et al., 2008). Studies which have presented severity categorically have observed that fifty percent of injured players recover from injury in one week or less (Bathgate, et al., 2002; Best, et al., 2005; Clark, et al., 1990; Durie & Munroe, 2000; Hughes & Fricker, 1994; Junge, et al., 2004; McIntosh, et al., 2004; McIntosh & Savage, 2005; McIntosh, et al., 2008; McManus & Cross, 2004). This is comparable to other contact sports such as rugby league and Australian rules football (Gissane, Jennings, Kerr, & White, 2002; Orchard & Seward, 2002). Other observations are an increase in the proportion of severe injuries at the elite level (Bathgate, et al., 2002; Best, et al., 2005) and a higher proportion of moderate injuries at other levels of play (Clark, et al., 1990; D. C. Hughes & Fricker, 1994; Junge, et al., 2004).

3.3.2.4 Injury during training

The reported training injury incidence rates are much lower than game injury rates. Training occurs in a more controlled environment than matches and opposed skills training makes up a smaller part of the training regimen (Brooks, Fuller, Kemp, & Reddin, 2005b; McIntosh, 2005b). However, a trend of increased severity of training injuries compared to match injuries has been observed at all levels of play (Babic, Misigoj-Durakovic, Matasic, & Jancic, 2001; Bathgate, et al., 2002; Brooks, et al., 2005a, 2005b, 2005c; Durie & Munroe, 2000; Junge, et al., 2004; McManus & Cross, 2004). It has been postulated that lower injury incidence in training compared to matches is associated with lower intensity levels and a reduction in the number and magnitude of contact activities in training (Durie & Munroe, 2000; McIntosh, 2005b). From this hypothesis it could be inferred that tackle injuries are not as large a problem during training as compared to matches. The higher incidence of non-contact injuries, such as muscle strains, occurring during training activities and high severity of non-contact lower limb injuries supports this hypothesis (Bathgate, et al., 2002). However, the incidence of

32 moderate and high severity injuries is higher for training than matches and contact injuries have been observed (Bathgate, et al., 2002; Brooks, et al., 2005b; Durie & Munroe, 2000). The occurrence of high severity injuries as a result of the tackle during training, which is a closed or more controlled environment when compared to a match, suggests that tackle injury risk may not be easily moderated.

3.3.2.5 Playing position and injury

The nature and frequency of a player’s exposure to match hazards is influenced by their playing position. Each position has a unique role in the team and the selection and development of players in specific positions depends largely on their physical characteristics and skills (International Rugby Board, 2005c). In a study of match trends, the IRB (2005a) found that forwards made fewer passes than backs, suggesting that they take the ball into contact more often, while backs, who are not involved in any set piece plays, are involved more often in ‘open play’ which is characterised by higher player velocities. Consequently, it is not surprising that there are differences in injury incidence for each player position, and between backs and forwards more generally. However, there is a lack of evidence to support that a representative pattern of injury exists according to position, and particularly position cohort (i.e. backs vs. forwards). Some studies have found that forwards have a higher incidence of injury than backs, especially loose forwards (flankers and No. 8) and the second row (Addley & Farren, 1988; Babic, et al., 2001; Bathgate, et al., 2002; Brooks, et al., 2005a). In other studies, backs were more often injured than the forwards, but the injury event was noted to be non- contact and injury severity was higher in the forwards (Brooks, et al., 2005c). A higher injury rate for forwards is often explained by an increase in the frequency of involvement in contact plays, such as tackles and ball contests, when compared to backs (Bathgate, et al., 2002; International Rugby Board, 2005a). It would appear from the data that injuries generally, and tackle injuries more specifically, do not conform to a certain pattern and present an equal injury risk for all players, particularly those entering contact.

33 3.3.3 Patterns of Injury in Rugby

Three criteria have been used to describe injury patterns in rugby union:

x Body region injured x Nature of injury x Event associated with injury

This section will present the injury trends that have been presented in the literature.

3.3.3.1 Body Region of Injury

The lower limb is the body region most often injured whilst playing rugby and was identified by almost every study as the most affected region. The proportion reported ranges from 31% in schoolboy rugby (Lee & Garraway, 1996) to 61% in senior rugby (Garraway, et al., 2000), however the majority of studies have observed approximately 40% of injuries affecting the lower limb (e.g. Brooks, et al., 2005a; Garraway & Macleod, 1995; D. C. Hughes & Fricker, 1994; Targett, 1998). In particular, the knee, thigh and ankle were the most commonly injured regions of the lower limb. The ankle and knee are susceptible to ligament sprains, especially during rapid changes of direction to evade the tackle contact. Injuries to these joints require a lengthy rehabilitation period and studies by Brooks et al. (2005a) and McIntosh et al. (2008) have found that injuries to the lower limb have the highest severity. The injuries affecting the thigh were most often muscle tears or strain injuries. Strain injuries occur during activities requiring the development of muscular force, and are most likely to occur during running, kicking and similar movements such as pushing or trying to maintain a body position against an external load (as in a tackle).

The upper limb is the second most injured body region and was associated with between 14 and 32% of all injuries (Best, et al., 2005; Junge, et al., 2004). The shoulder is the most injured structure of the upper limb (Brooks, et al., 2005a; McIntosh & Savage, 2005; McIntosh, et al., 2008). It is susceptible to injury through movement exceeding the normal joint range of motion. Such an injury may

34 result where a player’s body continues to move in a particular direction because of momentum while a force is applied to the upper limb in the opposite direction or when it is trapped and prevented from moving freely. Additionally, a force applied to an outstretched hand to break a fall transmits an axial load along the axis of the appendicular skeleton to the shoulder joint. The shoulder region is important during tackling and may be injured in these two loading modes.

The incidence of head, face and neck injury was greater than the incidence of shoulder injury in three studies of elite senior and one study of elite junior rugby (Bathgate, et al., 2002; Best, et al., 2005; McManus & Cross, 2004; Targett, 1998). The majority of head injuries that were identified in these studies were lacerations which required suturing. Rugby union presents a risk of spinal injuries and these most often occur in the scrum, tackle and ruck/maul (Quarrie, Cantu, & Chalmers, 2002). The focus of several case and cohort studies on these injuries has been previously noted. Only one serious neck injury, a career ending cervical dislocation attributed to scrum engagement, is reported in the injury surveillance literature (Best, et al., 2005). Catastrophic spinal injuries resulting from scrummaging have been investigated and, while the risk of neck injuries is still present in rugby, Carmody, et al. (2005) and Browne (2006) have reported that rugby union presents a similar or lower level of risk than other contact sports.

3.3.3.2 Nature of Injury

The nature of injury, which is the type or diagnosis of injury, can provide information on how an injury occurred. It is presented by van Mechelen et al. (1992) as one of six criteria for determining the severity of an injury. Over half the injuries in the research reviewed affected the soft tissue. These injuries were mainly muscle strains, ligament sprains, bruising and lacerations (Best, et al., 2005; McIntosh, et al., 2004; McIntosh & Savage, 2005). Ligament injuries occur in the highest proportion, accounting for between 16 and 44% of all injuries. Ligament injuries affected the knee (39%), shoulder (33%), ankle (19%) and cervical spine (8%) (Clark, et al., 1990). The average duration of recovery for these injuries ranged from 2 to 4 weeks. In addition to their acute symptoms, joint

35 injuries can be associated with long term sequelae such as early onset of osteoarthritis (Bahr, 2001; Buckwalter, 2003). The proportion of musculotendinous injuries reported in the literature varied widely. Between 8 and 51% of all injuries in the literature reviewed affected the muscular tissue.

Other injuries with high severity also occur in rugby union and may occur in the tackle. Fractures and dislocations are injuries with high severity and moderate to low incidence. Musculotendinous injuries (muscle strains and tendinitis etc., 8 to 46%) have a higher incidence than fracture and dislocation and generally a lower injury severity. The incidence rate of concussion reported in the research is in the range of 1.5 to 7.1 per 1000 playing hours. Compared to other levels of play, the rate of concussion is generally reported as being highest amongst youth and schoolboy players (3.9/1000 playing hours) (Durie & Munroe, 2000; Junge, et al., 2004; McIntosh, et al., 2004). The incidence rate of concussion in elite rugby is low. In a study of game and training injuries during the 2003 Rugby World Cup, only three concussions out of 145 injuries were observed in a total of 8373 player hours (Brooks, et al., 2005c). Access to medical support has been identified as a reason for the low rate of concussion at the elite level (Bathgate, et al., 2002), but the possibility of under reporting of concussion has also been raised (Best, et al., 2005; Durie & Munroe, 2000).

3.3.3.3 Event associated with injury

Establishing the cause of injury is identified as the second step of the sequence of injury prevention (van Mechelen, et al., 1992). On a rudimentary level, the number of potential causes of an injury can be narrowed by identifying the event that the player was involved in when the injury occurred. However, it has proven difficult to accurately identify the event associated with injury in rugby union: injury surveillance studies have reported a high proportion of injuries occurring in an unknown phase of play (between 21 and 38%) even when using trained primary data collectors to record injury information (McIntosh, McCrory, Finch, Best, & Chalmers, 2005; McIntosh, et al., 2008).

36 Within the published literature, more rugby injuries occur during contact events than during non contact events (Best, et al., 2005; Brooks, et al., 2005a). When considering the event associated with injury, the tackle accounts for most injuries, followed by ruck and maul, overexertion and stepping or cutting (Bathgate, et al., 2002; Best, et al., 2005; Garraway, et al., 2000; Garraway & Macleod, 1995; McIntosh, et al., 2008; McManus & Cross, 2004). Injuries occur less frequently during restarts (the scrum and line-out). Within the tackle, a player is more likely to be injured whilst being tackled (between 13 and 30% of injuries) than while tackling (between 9 and 23% of injuries). The ruck and maul are not often differentiated in the literature. Combined they account for between 4 and 25% of injuries. Muscular overexertion injuries (sprinting, kicking, lifting, or gym injuries) ranged between 3 and 11% whilst injuries sustained while cutting or twisting to pass/accelerate were generally associated with less than 5% of the total injuries (Best, et al., 2005; Brooks, et al., 2005a, 2005c; Clark, et al., 1990; Durie & Munroe, 2000; Garraway, et al., 2000; McIntosh, et al., 2008). The scrum and side stepping/cutting are aspects of rugby which may lead to severe injuries, specifically spinal cord injury (SCI) or anterior cruciate ligament (ACL) rupture.

3.3.4 Foul Play

The physical nature of rugby union can be used as cover for negligent or malicious play. Several authors have noted that players may seek to take advantage of the unstructured, contact nature of the tackle to purposefully inflict harm on an opponent. Such events may occur to gain a match advantage or in retaliation to events on the field. The IRB’s playing charter and laws of rugby emphasise that the spirit in which the game is played is important. The charter states that a player:

“will not wilfully or maliciously take advantage of the contact nature of the game to inflict injury to an opponent”

(International Rugby Board, 2005b, 2005c).

Dangerous play in the tackle is addressed in Law 10.4 (International Rugby Board, 2005b). Sanctions against foul play have been included in the rules of rugby since

37 1878 (Grayson, 1996), most likely because these events pose an unacceptable risk of injury.

Law 10.4 (e) Dangerous tackling.

1. A player must not tackle an opponent early, late or dangerously. 2. A player must not tackle (or try to tackle) an opponent above the line of the shoulders. A tackle around the opponent’s neck or head is dangerous play. 3. A ‘stiff-arm tackle’ is dangerous play. A player makes a stiff-arm tackle when using a stiff-arm to strike an opponent. 4. Playing a player without the ball is dangerous play. 5. A player must not tackle an opponent whose feet are off the ground.

Law 10.4 (g). Dangerous charging.

1. A player must not charge or knock down an opponent carrying the ball without trying to grasp that player.

Law 10.4 (f). Tackling the jumper in the air.

1. a player must not tackle nor tap, push or pull the foot or feet of an opponent jumping for the ball in a line-out or in open play.

A number of studies indicate that injuries do occur in rugby because of foul play and that the incidence of these injuries is relatively low, between 4 and 6% (Bathgate, et al., 2002; Brooks, et al., 2005a). Other research supports a higher proportion of injuries associated with foul play (Bird, et al., 1988; Davies & Gibson, 1979; Inglis & Stewart, 1981). In their study of tackle injuries, Garraway, et al. (1999) investigated player anger and player response to anger and hostility using a psychological questionnaire. They found no difference in these traits between injured and non-injured players. In his article, Grayson (1996) describes an instance where a player had his jaw intentionally broken in a tackle, while Davies and Gibson (1978) attribute up to 32% of injuries to punching, kicking or gouging, events that could be described as personal violence offences. However, a weakness of injury surveillance research is that it does not provide reasons for the

38 play being considered illegal, outside of obvious personal violence events (e.g. punched, kicked, gouged), or on who’s judgement the adjudication is based (i.e. if the event was identified and penalised by the referee or based on the opinion of a player or data recorder). Studies using player self report for injury data collection reported a higher proportion of foul play than studies that obtained injury data through medical staff. This suggests that a standard definition for foul play is required.

3.3.5 Playing Conditions

Playing conditions have been suggested as an injury risk factor in a number of sports, including rugby union (Davidson, 1987; Orchard, 2002). Playing conditions can be defined as the environmental circumstances under which a match is played. They’re influenced by the weather, including ambient temperature, humidity and precipitation, and the firmness and trueness of the playing surface (Alsop, et al., 2005; Orchard, 2002). In his review of the topic, Orchard (2002) observed that changes in weather conditions would have an effect on the playing surface and alter the shoe/surface interaction, an interface which has been hypothesised as a potential aetiological factor.

However, there is disagreement in the literature over the influence of weather and playing conditions as independent risk factors for injury. Inglis and Stewart (1981) and Davies and Gibson (1978) reported that 50 and 60% of injuries respectively occurred when the playing field was ‘soft’. Conversely, other authors have found a higher injury incidence on harder grounds, or suggested hard grounds as a risk factor for injury (Alsop, et al., 2005; Davidson, 1987; Lee & Garraway, 2000). At the time that this research commenced, objective measures had not been used to assess ground hardness as a dependent factor for injury. Subsequently, Takemura, Schneiders, Bell and Milburn (2007) recorded ground hardness during an injury surveillance study, but could not reach a conclusion that ground hardness was related to injury in favour of other factors. The involvement of playing conditions in injury aetiology is ambiguous and further research describing the conditions at the time of injury is required.

39 3.3.6 Summary

Rugby union has long been a target for injury surveillance research, though differences in data collection methods have made comparisons between studies difficult. The tackle has consistently been identified as the event which is most often associated with injury. The tackle has a high match frequency compared to other events, accounting for between 50 and 60% of match events, or approximately two hundred tackles per match at the elite level. When the frequency of match events are taken into account, the tackle remains the leading cause of injury.

Considering the results of epidemiological research provides a general overview of risk factors for injury in rugby union. It has been a general trend that injury rates increase with level and grade of play and for the lower limb to be the most often injured body region. The knee, ankle, shoulder and head are amongst the injured structures identified most commonly. Sprains and strains are the most common nature of injury, though concussions, especially in younger age groups, and fractures and dislocations occur at lower incidence rates. There is disagreement regarding the effect of playing position on injury incidence, however, most studies have observed that forwards have a higher injury incidence than backs. Forwards are involved in more contact events, where the majority of injuries have been recorded, during a match. Injuries arising from foul play can occur in the tackle but generally account for a small proportion of all injuries (4-6%).

While informing the type of injuries and other information that may be useful in describing tackle injury situations, a more complete understanding of injury aetiology and potential risk factors is required. The following chapter will evaluate evidence for specific injury risks that have been presented in the literature.

40 3.4 Tackle Injuries

The tackle is a complex, intentional collision event that is vital to on field success in rugby union. The most frequently occurring match event in rugby, it is an open skill, occurring in an unstable, dynamic game environment with varying spatial and temporal constraints (Magill, 1998). Match conditions are dependent upon the actions and reactions of individuals, the game state and environmental conditions. As a result, tackles can involve any number of players engaging with the Ball- carrier in different sequences and from different directions. The collision force is dependent, amongst many factors, on the speed of the players prior to impact, the number of players involved, the extent of the contact between players and their ability to prepare for the collision and any subsequent impact while maintaining possession of the ball for their team. The interaction between players is monitored by an on field referee who adjudicates that a tackle event is within the rules governing fair play. The aetiology of injuries in events like the tackle is multi- factorial, likely as a result of the dynamic environment and unpredictable response of players (Meeuwisse, 1994).

The general injury patterns affecting rugby union players were presented in section 3.3.2 to present tackle injuries in the broader context of rugby injury incidence. The research identified the tackle as the match event with the highest injury incidence and indicates that the Ball-carrier is at a higher risk of injury than the Tackler. In addition to having the highest incidence rate; the tackle also has high injury severity (Brooks, et al., 2005a; Garraway & Macleod, 1995; McIntosh, et al., 2008; McManus & Cross, 2004). This section of the literature review will summarise current research in the area of tackle and tackle injuries, presenting the aspects of the tackle that have been proposed as potential injury risks, the relationship between tackle frequency and injury.

41 3.4.1 Focussed Tackle Research

At the time that this research commenced there was little focussed research specifically examining tackling technique and/or injury aetiology in the tackle. Ten studies had described the circumstances of tackling injuries in rugby in an attempt to identify potential risk factors. Five case studies reported circumstances of spinal injuries occurring in the tackle in South African rugby from the perspective of a treating physician (Scher, 1978, 1981, 1983a, 1983b, 1991b). One case control study examined risk factors for tackle injuries in an adult population (Garraway, et al., 1999) and two studies had detailed the characteristics of tackle injury events from match video (McIntosh, Savage, et al., 2005; Wilson, et al., 1999). One study investigated the kinetics of tackling (Trewartha & Stokes, 2003) and a further study attempted to investigate the physiological response to repetitive impacts sustained during rugby (Takarada, 2003).

In a series of case studies in South African rugby, Scher (1978, 1981, 1983a, 1983b, 1991b) reported the circumstance of injury to patients presenting to a hospital spinal cord unit. Three of these studies investigated injuries to the Ball- carrier (Scher, 1983a, 1983b, 1991b), one described an injury to a Tackler resulting from axial compression (Scher, 1981). A fifth study described fourteen injuries; four affecting the Tackler and ten to the Ball-carrier (Scher, 1978). As a result of these observations the author identified three mechanisms of injury:

x poor tackling technique x tackles around the neck x tackles involving two (2) Tacklers

Poor tackling technique was defined as a tackle that resulted in the Tackler colliding head first with the Ball-carrier’s body or with the ground. The author observed that this placed the player at risk of a vertebral compression fracture or dislocation of the vertebrae (Scher, 1978, 1981). He recommended four preventative measures:

42 x Strength training to develop natural muscle tone of the neck muscles x Coaching the Tackler to properly track the Ball-carrier x Coaching the Tackler to keep their head up when tackling x Coaching the Tackler to tackle with their head to the side of the Ball- carrier

Scher (1978) observed that injuries to the Ball-carrier were associated with high tackles and tackles involving more than one Tackler and recommended changes should be made to the rules to sanction tackles above the line of the shoulders.

Garraway and Lee (1999) conducted a case control study of tackling injuries in an adult playing population. Injury data were collected prospectively by a trained data recorder and additional data (lifestyle habits, match preparation, training attendance, and illness) were collected retrospectively using a questionnaire. They recorded seventy eight tackling injuries over one season and compared these injured players to controls with a similar playing position who participated in the same game. They identified the direction of the tackle origin and awareness of the tackle as common factors amongst the injured cases. In addition, they found that the extent of match preparation, and previous coaching in proper tackling technique and practising tackling skills did not contribute significantly to tackle injuries. Lifestyle factors such as alcohol consumption before the match and suffering minor illness were also not associated with an increased injury risk.

Wilson, et al. (1999) used the analysis of 28 ‘injury’ events from video to supplement injury surveillance data. The events were evaluated by two analysts to describe the circumstances of the injury, using a qualitative analysis protocol, in terms of the following variable groupings:

x the role of the player x player action at the time of injury x nature of the tackle x key factors in the tackle situation x injury mechanisms

43 The analysis schema that was used in the study by Wilson and colleagues is presented on page 90 (Figure 3.10). For the purposes of their study, an injury was defined as one which resulted in the match being stopped for the player to receive medical attention. Impact with other players was the most frequently observed mechanism of injury (61%), followed by impact with the ground (21%) and intrapersonal impact (twisting etc., 18%). They found that the majority of injuries to the Ball-carrier affected the lower limb and occurred when the player was falling to the ground. When falling to the ground, the authors reported that ground contact was most often associated with injury and hypothesised that players who reduced the effect of the impact by ‘turning in the tackle’ or ‘controlling the impact’3 were less injured. While this may be supported by anecdotal evidence, it is not clear how the authors reached this hypothesis in the absence of evaluation of incidents where injuries did not occur and this is a limitation of this study. The Tackler was more likely to be injured during an impact with another player and the body regions most affected were the head and face, and the shoulder. For the majority of cases (70%) the player was moving (either running or diving) rather than being stationary when the injury occurred. However, the proportion of incidents associated with a player being stationary (30%) indicate that injuries may occur in this situation. Similar to Scher (1978, 1991b), the authors recommend more stringent refereeing and athlete preparation as preventative measures, noting that not all of the incidents investigated were legal or performed with a proper technique. It is not clear that all events that were analysed in this study resulted in an injury as prospective injury data were not presented and the affected player did not leave the field in the majority (80%) of events.

McIntosh, et al. (2005) recorded collision characteristics for tackles causing injury from video of youth (13 to 20 years) rugby matches. They defined an injury as an event where a player did not get up to resume play immediately and recorded the body region struck and the striking object. Their findings indicate that the head and

3 The notion of controlling or managing the impact force by ‘giving’ with the impact is similar to attenuating the impact by limiting changes in acceleration caused by the impact force (Newton’s second law). The rate of deceleration, and resultant change in linear momentum, can be minimised by minimising the net force applied to a body.

44 neck were regions most commonly injured (18%), followed by the shoulder (15%) and face (13%). The two most frequent objects to strike a player were the ground (19%) and the shoulder (11%). The study has a number of limitations. No differentiation was made between results for making and receiving a tackle. The definition used to identify ‘injury’ in this study needs to be considered in interpreting the results, as players who appear in discomfort following a tackle may not be injured but only temporally impaired. Additionally, data were not presented for events that did not result in an injury and, consequently, this may be reflected in the proportion of injuries. For example, the head, face and neck region was found to be the most commonly affected region in tackles resulting in an ‘injury’. This is significant because it cannot be discounted that players who receive a knock to the head may more likely appear in discomfort and, therefore, the region may be over represented compared to other ‘injuries’ under the definition that was used in this study. The results of the research of McIntosh, et al. (2005) contributed significantly to the development of the protocol that is described in this thesis.

The kinetics of tackling has been evaluated in two studies utilising similar methods. Trewartha and Stokes (2003) and Pain, Tsui and Cove (2008) measured the impact pressure applied to the Tacklers shoulder during tackling while controlling for speed. They reported mean impact forces equivalent to 1 body weight for a slow tackle condition increasing to 1.3 to 1.5 body weights for a fast or running tackle condition when affecting a shoulder style tackle. Trewartha and Stokes (2003) measured the centre of pressure within 1cm laterally and 1 to 3cm anteriorly of the acromioclavicular joint (AC joint). The authors reported that impact pressures were high as the forces were applied over a relatively small area. Pain et al. (2008) observed a “distinct force peak” over the AC joint. A literature search failed to identify the force required to rupture the ligaments of the AC joint. However, as no injuries were observed during these experiments it can be assumed that the reported figures are within tolerance levels. The method of identifying the location of the AC joint was not described and the speeds of the fast and slow conditions were not quantified. Further, no information is given on the number of trials, the type (tackle bag or another player) or position of the target and whether that target was

45 moving at the time of the tackle. It is, therefore, difficult to judge the validity of the figures reported with regard to match play. Additionally, the characteristic tackle type employed in rugby has not been investigated so it is not known how representative the shoulder tackle is of match tackling technique.

Following the development of the protocol that was developed in this thesis, additional investigations of the circumstances of tackling and tackling injury have been published. Two of these studies utilised the qualitative analysis protocol which was developed in this research (Fuller, et al., 2010; McIntosh, Savage, et al., 2010). The protocol that was used in the third study was used to inform the development of this research (Quarrie & Hopkins, 2008). Finally, one study was conducted investigating shoulder forces experienced during the active shoulder tackle. The study found a mean maximum tackle force at the shoulder of almost two body weights and no difference in force according to playing position, playing experience or body mass index (Usman, McIntosh, & Fréchède, 2011).

3.4.2 Injury Surveillance

The tackle has the highest incidence and severity of injury in rugby union. The effect of the injury definition on the rates and proportions of injuries was reported in section 3.3. A comparison of tackle injury proportions from several studies using different injury definitions is presented in Table 3.4. The criteria for inclusion in the comparison were that the study presented the proportion of injuries to both the Tackler and Ball-carrier separately and that it was clear whether the study included training injuries in the proportions reported. The average proportion of injuries incurred while being tackled was 24.4% (SD = 4.2). The average proportion of injuries incurred while tackling was 15.6% (SD = 4.6). The value of the standard deviation indicates some variation in the sample. However, the mean and standard deviation of the proportions presented in Table 3.4 do not diverge when calculated for the differences in injury definition (match vs. session) or for studies including training injury compared to those that do not, suggesting that the effect of differences in injury definition upon the proportion of tackle injuries recorded is

46 not substantial. Therefore, all studies reporting tackle injury have been reviewed in this section, regardless of the injury definition that was used.

Being Tackling Injury Training injuries tackled (%, all definition included in Authors (%, all injuries) reported injuries) proportions? Best et al 19.1 20.6 Session No (2005) Brooks et al 23 13 Session Yes (2005c) Clark et al 26 14 Session Yes (1990) Durie & 22.0 18.5 Session No Munroe (2000) Garraway & 27 22 Session Yes McLeod (1995) Hughes & 30.8 19.5 Session Yes Fricker (1994) McIntosh et 29.8 12.3 Match No al. (2004) McIntosh & 21.8 10.2 Match No Savage (2005) McIntosh et 20.4 9.9 Match No al. (2008) Average 24.4 15.6

Table 3.4: A comparison of the proportion of tackle injuries according to the injury definition used in injury surveillance studies in rugby union.

A summary of tackle injury data from epidemiology studies conducted in rugby across all levels of play is presented in Table 3.5. The results of the research provide evidence that between 34 and 60% of all injuries occur in the tackle, the highest proportion of tackle injury was recorded in elite players and the lowest proportion was recorded in a cohort of senior amateur players. Examining the role of the injured player within the tackle event (i.e. Ball-carrier or Tackler), all but one study has found that a higher proportion of tackle injuries occur to the Ball-

47 carrier than to the Tackler and that the proportion of injuries to the Ball-carrier increases with level of play.

The most common injuries in the tackle are sprains and strains, fractures, dislocations and concussion (McIntosh, et al., 2008). The most common nature of injury varies according to the study, the level of play targeted by the investigation, and between the Ball-carrier and Tackler. Brooks et al. (2005a) identified haematoma as the injury nature with the highest incidence and knee ligament as the injury with the highest severity amongst Ball-carriers in English professional rugby. In the same study, concussion had the highest incidence and shoulder ligament sprain or dislocation had the highest severity when tackling. A study of youth rugby (under 20) by McIntosh, et al. (2008) identified concussion as the most common injury for both the Ball-carrier and Tackler. Shoulder sprains occurred in similar proportions to both players while superficial injuries (bruising and abrasions) to the knee and shoulder were also found to cause the Ball-carrier to miss matches. Superficial injuries, such as haematoma, bruising and grazing, were an injury problem only in youth rugby and did not cause players from older playing cohorts to miss matches.

In general, joint sprains were responsible for the most time lost amongst the studies reviewed. Sprains generally affected the shoulder and knee joints. The shoulder is known to be at risk of injury particularly when tackling and, in rugby, both the acromioclavicular and glenohumeral joints are commonly injured structures in the region and have high injury severity (Brooks, et al., 2005a; Headey, Brooks, & Kemp, 2007; McIntosh, et al., 2008). In their study investigating the epidemiology of shoulder injuries in professional rugby union, Headey et al. found that the injuries with highest severity were glenohumeral joint dislocations and instability (subluxation) which were most often sustained while tackling another player, while acromioclavicular ligament sprains mostly affected the Ball-carrier. Conversely, McIntosh et al. (2008) found that glenohumeral dislocations occurred in a slightly higher proportion to the Ball-carrier than to the Tackler.

48 Study authors Playing Definition of injury Tackle Tackle Tackle population injuries injuries injuries as % all sustained sustained injuries tackling being (% all tackled injuries) (% all injuries) Durie & School boy left the field because of an 40% 46% 54% Munroe (2000) injury or complained of an (18%) (22%) injury at the completion of a match Nathan et al. School boy prevented the player from 47% 47% 53% (1983) returning to rugby for at (22%) (25%) least 7 days after the injury Nathan et al. Senior an injury was taken to be 34% 46% 54% (1983) the presence of pain, (16%) (18%) discomfort, or disability arising during and as a result of playing in a rugby match Bird et al. Mixed level caused the player to seek 40% 47% 49% (1998) medical attention or to (18.8%)* (19.6%)* miss at least one scheduled game or team practice Clark et al. Senior prevented a man from 40% 35% 65% (1990) playing rugby for 7 or (14%) (26%) more days or that required medical or surgical treatment Garraway & Senior an injury sustained on the 49% 45% 55% Macleod (1995) field during a competitive (22%) (27%) match, during a practice game, or during other training activity directly associated with rugby football, which prevented the player from training or playing rugby football from the time of the injury or from the end of the match or practice in which the injury was sustained Inglis & Stewart Mixed level attended the A(accident) & 44% Not Not (1981) E(emergency) department reported reported of Christchurch hospital after playing rugby Hughes & Senior prevented a player from 50.50% 39% 61% Fricker (1994) (Amateur) playing or training or that (19.5%) (31%) required ‘special medical treatment’

49 Study authors Playing Definition of injury Tackle Tackle Tackle population injuries injuries injuries as % all sustained sustained injuries tackling being (% all tackled injuries) (% all injuries) Bathgate et al. Elite an injury was defined as 59% Not Not (2002) an event that forced the reported reported player to either leave the field or miss a subsequent game Best et al. Elite left the field or missed at 39.6% 54% 48% (2005) least one match (20.6%) (19%) Brooks et al. Elite any injury that prevents a Not Not Not (2005a) player from taking a full reported reported reported part in all training and match play activities typically planned for that day for a period of greater than 24 hours from midnight at the end of the day the injury was sustained Brooks et al. Elite any injury that prevents a 36% 37% 63% (2005c) player from taking a full (13%) (23%) part in all training and match play activities typically planned for that day for a period of greater than 24 hours from midnight at the end of the day the injury was sustained Targett (1998) Elite prevented a player from 46% Not Not taking full part in two reported reported training sessions, from playing the next week, or one that required special medical treatment (such as suturing or special investigation)

Table 3.5: Proportion of tackle injuries from epidemiological studies of rugby union * Support players (additional Tacklers) accounted for 4% of injuries

The mechanisms of injury described in the literature for glenohumeral dislocation indicate that these injuries normally arise from direct trauma to the glenohumeral head or indirect trauma through excessive abduction and internal rotation (Hoelen,

50 Burgers, & Rozing, 1990; W. B. Kibler, 2001). Several studies also identify a fall to an outstretched arm or to the elbow as a potential mechanism of injury (Hoelen, et al., 1990; Hulstyn & Fadale, 1997; Kuriyama, Fujimaki, Katagiri, & Uemura, 1984) though studies have found that this is a minor cause of injury in younger patients compared with a direct blow to the shoulder (Kroner, Lind, & Jensen, 1989). The mechanism for AC injury is identified as direct trauma to the AC region, such as experienced during a fall to the point of the shoulder, particularly when the shoulder is adducted (W. B. Kibler, 2001; Lemos, 1998). Garraway (1999) observed that it was the cause of injury in 7 of the 12 tackled players and that 5 of 7 tackling players fell to the ground as a result of the tackle and injured their shoulder. The tackle impact centre of pressure identified by Trewartha and Stokes (2003) would suggest that it is possible for either dislocation or AC ligament injury to occur during either the primary tackle impact or ground contact.

In their study of knee injuries in professional rugby union, Dallalana, Brooks, Kemp and Williams (2007) found that the majority of match knee injuries occurred in contact. This is in contrast with the findings of studies in rugby and other sports that the majority of serious knee injuries occur in non-contact situations, e.g. during rapid changes of direction, such as side stepping and cutting (McIntosh, et al., 2008; Olsen, Myklebust, Engebretsen, & Bahr, 2004; Orchard, Seward, McGivern, & Hood, 2001). Dallalana and colleagues found that almost 75% of knee injuries occurring in the tackle were sustained by the tackled player. The Ball- carrier suffered seven times as many meniscal and chondral injuries, four times as many injuries to the medial collateral ligament, all injuries to the posterior collateral ligament and one and a half times as many anterior cruciate ligament injuries. They hypothesised that injury was related to the unpredictability of the tackle impact and limited options to avoid injury. This research does not describe how the injuries occurred in the tackle or elaborate on the factors that were considered unpredictable.

The majority of neck injuries in rugby union occur in the scrum and tackle (McIntosh, McCrory, Finch, & Wolfe, 2010; Nathan, et al., 1983; Quarrie, et al.,

51 2002; Rotem et al., 1998). While the scrum has been seen as the event posing the highest risk for cervical injury, several authors have noted that severe spinal injuries are occurring more frequently in tackle situations (Quarrie, et al., 2002; Scher, 1991a). In a study of hospital admissions from rugby league and rugby union, Rotem et al. (1998) found that tackles were the leading cause of spinal injury. In Scher’s (1978, 1983a, 1991b) series of case studies, he reported the occurrence of serious neck injuries in the tackle in rugby and more recent research suggests that there is also a potential risk of injury in this phase of play, particularly in multiple Tackler situations (Carmody, et al., 2005).

The trend towards increased injury incidence in higher grades and levels of play of rugby union has been discussed previously (Durie & Munroe, 2000; Garraway & Macleod, 1995; McIntosh, et al., 2008). From the proportion of tackling injuries presented in Table 3.5 it is apparent that there is no clear pattern of tackle injury by level of play. However, these results do not account for match exposure. The two studies to have examined tackle injury incidence rates have reported conflicting findings. Two studies conducted by Noakes and colleagues found that a higher proportion of tackle injuries occurred to schoolboy players compared to their earlier research in adult players (Clark, et al., 1990; Nathan, et al., 1983). They concluded that the adult players were more proficient at tackling than schoolboy rugby players. In contrast, McIntosh, Savage and Dutfield (2008) reported injury incidence in youth and adult players over the same season where a tackling injury incidence rate at the schoolboy level was lower than that measured in a cohort of senior players (2.6 and 4 injuries per 1000 player game hours respectively).

Clark et al. (1990) suggested that their finding demonstrated a disparity between the tackling skills of the two groups of players, with younger players not as adept in their tackling skills. McIntosh et al. (2008) also stated that poor tackling technique was likely to result in an increased injury risk, as relating to all players and not just in youth. Other authors have supported the assertion that poor tackling skills likely result in an increased injury risk (Garraway, et al., 1999; Scher, 1978). The coaching literature specify that technique must be instinctive and young

52 players who are still developing the skills and confidence to tackle safely and effectively may be at an increased risk of injury (NZRU & ACC, 2005b). Injury risk may be increased in older players as a result of increased impact forces associated with increased body mass of the opponents and an increased game speed, similar to the mechanism proposed by Brooks et al. (2005a) in describing a higher tackling injury risk in the professional rugby backs.

Video analysis of tackle injuries confirms the head and neck (36%), shoulder (36%) and knee (22%) as the main body regions injured (Wilson, et al., 1999). While direct impact with particular body regions during the tackle have been identified as a risk factor for injury such as shoulder and neck injuries, one aspect that has not been investigated is the frequency of contact by body region. The study of Wilson et al. (1999) presented the location of impact according to whether the impact was to the torso or to the legs. They found that marginally more impacts occurred to the upper body than to the lower body (57% and 43% respectively) but suggested that further research was required to determine the frequency of impacts in non-injury events.

In discussing the findings of their research, several authors have recommended that the tackle, particularly events which do not lead to injury, should be investigated (Bird, et al., 1998; Garraway, et al., 1999; Lee & Garraway, 1996; McManus & Cross, 2004). Injury trends that have been identified for the tackle are similar to what has been reported for rugby union more generally. Aspects such as the level of play, the region of the impact, whether the player fell to the ground and the body region struck in the secondary impact represent important information describing the risk of injury in the tackle.

3.4.3 Tackle Frequency and Injury

The frequency of match events was reviewed in section 3.2. In summary, studies of match event frequency have shown that the number of tackles per match is greater than other events, accounting for approximately 50 to 60% of match events and 35 to 60% of all injuries across all levels of play (Addley & Farren, 1988; Bathgate,

53 et al., 2002; Fuller, Brooks, et al., 2007; McIntosh, Savage, et al., 2005; Quarrie & Hopkins, 2007). Fewer injuries were associated with set piece plays, such as the scrum and line-out, which also occur less frequently in a match. It is possible that high injury rates for the tackle are a product of high event frequency and that other events occurring less frequently pose a greater injury risk. At the time that this research commenced, two studies had compared injury incidence and event frequency in rugby union (Fuller, Brooks, et al., 2007; McIntosh, Savage, et al., 2005). These two studies were reviewed to determine the effect of event frequency on injury rates.

In a pilot study utilising qualitative analysis to investigate the tackle, McIntosh, Savage and Nicholson (2005) enumerated match events from video of youth rugby (under 15, under 18 (schoolboy) and under 20 (colts)). Where an injury was deemed to have occurred, the preceding match event was identified and recorded. Injury rates were presented as the number of injuries per 1000 events. For the purposes of their study, an injury was defined as an event that:

x caused visible physical discomfort; or x resulted in the player leaving the field; or x resulted in the player receiving on field attention from a physician or trainer (medical aid)

The results of the study indicated that the tackle had the highest rate of injury in all of the levels of play studied with a mean rate of 5.3 injuries per 1000 tackles. Assuming a frequency of between 120 and 150 tackles per game in youth rugby, this is approximately one injury every one to two games (0.64 to 0.8 injuries per game). The corresponding tackle injury incidence for all injuries in this population was 27.9 per 1000 player hours, or 0.92 injuries per sixty minute game (McIntosh, McCrory, et al., 2005). The maul had the second highest rate of injury (3 injuries per 1000 mauls) followed by the ruck (2.5 injuries per 1000 rucks) and the scrum (2.3 injuries per 1000 scrums).

Fuller et al. (2007) performed a similar study, enumerating phases of play in professional rugby. They found that, while tackles had a high injury rate, the scrum

54 (8 injuries per 1000 scrums) and collisions, which they defined as tackles without the use of arms (10 injuries per 1000 collisions), possessed the highest rate of injury per event. Tackling without the use of arms is defined as dangerous play in the laws of the game of rugby union (International Rugby Board, 2005b). Law 10.4g states that:

“A player must not charge or attempt to knock down an opponent carrying the ball without trying to grasp that player.”

Therefore, the events identified by Fuller et al. (2007) are known to have an increased risk of injury. The authors reported that there were, on average, fifteen collisions per match which equates to one injury in seven games. There are far fewer scrums per game than tackles and the injury incidence for scrum injuries is not high. However, the increase in the incidence of scrum injuries when considered by event frequency demonstrates the effect event frequency can have on injury incidence. It also demonstrates the presence of different injury problems at different levels of play. Variations in the rules of scrummaging could explain the higher rate of scrum injury in professional rugby union between the two studies, which were performed in different populations. The injury incidence rates for tackling expressed by event (6.1 injuries per 1000 tackles) and exposure (33.9 injuries/1000 player-hours) are similar to those recorded by McIntosh et al. (2005). Based on the results of these studies the tackle retains a high risk of injury when injury rate is corrected for event frequency.

3.4.4 Risk Factors for Tackle Injury

The preceding sections of this review have presented injury trends that have been identified in rugby union and in the tackle more specifically. In discussing injury trends, many authors have identified factors that are common to injury events, or expressed an opinion on factors contributing to injury in the tackle. Some of these factors are evidence based and others appear to be based on anecdotal wisdom. Risk factors for tackle injury are useful in developing a description of injury situations and poor skill execution. The risk factors for tackle injury that have been identified in the literature are:

55 x high tackles and foul play x stability (Base of support) x awareness of the tackle x direction of tackle origin x speed of the players prior to the tackle x Tackler engagement and tackle type x collisions with the ground and other players x field position x muscle damage caused by repetitive tackles x level of play and playing position x weather and pitch conditions

With the exception of high tackles and foul play, which were reviewed in section 3.3.4, the risk factors that have been presented in the literature and supporting evidence for professional knowledge and commonly held beliefs will be presented in this section.

3.4.4.1 Stability and balance

Resisting the work created by the force applied by the Tackler is related to maintaining stability in dynamic balance. Tackles occurring at high speed and originating from behind the tackled player have been highlighted as an important factor in injuries occurring in rugby union (Garraway, et al., 2000). The risk posed to a Ball-carrier when they are tackled with one or both feet not in contact with the ground and unable to resist antagonist action has also been noted (Scher, 1991b). Stability is defined as the resistance of a body to disruptions in static or dynamic balance (Elliott & Wood, 1995; Kreighbaum & Barthels, 1996). Dynamic balance is the ability to maintain equilibrium, or resist changes in linear and angular acceleration, during movement at a constant velocity (Hall, 2006). Gait variables (stride length and stride frequency) can be altered to increase speed or to increase stability. There are three factors that affect the stability of an object. First, the player with the greatest body mass is less likely to be affected by a perturbation,

56 described by Newton’s first law, the law of inertia. The second factor is the position of the centre of gravity relative to the base of support. To maintain stability in static and many dynamic situations the centre of gravity of the body must be kept low and within the base of support, the portion of the body in contact with the ground (Hall, 2006; Hamill & Knutzen, 1995). Therefore, stability can be improved by altering the shape of the body by lowering the centre of mass towards the ground and widening the position of the feet in relation to each other (Kreighbaum & Barthels, 1996).

If an impact is expected in a dynamic situation, the Ball-carrier might compensate by leaning towards the expected antagonist, taking their centre of mass to the limit of their base of support. When the force is applied and the centre of mass is decelerated it remains within the base of support (Elliott & Wood, 1995). Leaning towards and opposing the impact reduces the ability of the player to ‘give with the impact’ and increases the magnitude of the collision. Many tackles occur when both the Ball-carrier and Tackler are running and the majority of these do not result in injury. Therefore, the methods that the Ball-carrier and Tackler use to maintain stability and balance in the tackle should be investigated.

3.4.4.2 Awareness

Unexpected collisions have been associated with serious and catastrophic injury in a number of sports, including skiing, soccer, baseball and cricket (Boden, 2005; Orchard, James, Alcott, Carter, & Farhart, 2002). Awareness of an opponent and an impending collision can assist the player in preparing for the impact or to take evasive action. Andersen et al. (2003) evaluated player awareness of tackles in soccer by assessing head position. Garraway et al. (1999) and Scher (1991b) both used the direction of tackle origin synonymously with awareness, where the tackle originating from in front of the Ball-carrier was adjudged to be within the player’s field of view. In their case control study of tackle injuries, Garraway et al. (1999) claimed that the Ball-carrier “might have been only vaguely aware” of the tackle in more than 50% of injury cases because of the direction of tackle origin. Scher (1978, 1991b) concluded that awareness of a tackle was a risk factor for cervical

57 spine injuries after observing that serious cervical spinal injuries occurred in tackles originating from behind the Ball-carrier’s field of view. The author argued that awareness of an impending tackle allowed for preparatory muscular contraction which could decrease the trauma sustained in the cervical region. Awareness of a tackle may allow a player with appropriate strength and sufficient training to maintain balance, through principles of stability, during the tackle impact.

3.4.4.3 Direction

The direction from which the tackle originates (tackle direction) has been used to describe the tackle in epidemiology research and video analysis. Tackle direction is usually defined with respect to the Ball-carrier according to the anterior-posterior and medial-lateral axes with respect to the Ball-carrier (e.g. Wilson, et al., Figure 3.2). However, there are conflicting findings in the literature regarding a causal association between tackle direction and injury to the Ball-carrier. This may be attributed, in part, to the different time periods over which the studies were conducted and associated variations in tackling and playing style. The comparison is further complicated because, of the four studies describing the relationship between tackling injury and tackle direction at the time this research commenced, only two studies have clearly presented data for the Ball-carrier and Tackler separately.

In his studies of serious cervical spinal injuries, Scher observed that cervical spine injury resulted from hyperextension of the neck and argued that tackles originating from behind the Ball-carrier presented an increased risk of injury (Scher, 1978, 1991b). Conversely, Brooks, et al. (2005a) recorded that 51% of injuries to the Ball-carrier in English professional rugby were associated with side-on tackles and 34% of injuries were associated with front-on tackles. For the Tackler, 56% of injuries were sustained while tackling head on and 38% while tackling from side- on.

Of the two studies that did not differentiate between injuries to the Ball-carrier and Tackler, Garraway et al. (1999) found that 52% of tackles resulting in an injury

58 originated from behind the Ball-carrier or in their field of peripheral vision and Wilson et al. (1999) found that front-on tackles were observed nearly three times more commonly in the injury events than side-on tackles or tackles made from behind. In contrast to Scher’s findings, Garraway found that the Tackler was more often injured than the Ball-carrier when tackling from behind the Ball-carrier.

Figure removed due to copyright restrictions

Figure 3.2: Direction of the tackle (Wilson, et al., 1999)

The contrasting findings and different presentation of the data make it difficult to reach a conclusion that tackle direction may present an independent injury risk factor. Logically, tackles originating from behind the tackled player could represent a higher injury risk because the player may not be able to prepare for the impact. Should this be true, then tackle direction would be an indicator of awareness, as discussed in the preceding section (awareness). However, Scher’s research used case study methodology to investigate cervical spinal injury and it should be noted that many of the injuries presented were the result of high tackles where this mechanism of injury is common and related to application of force to the anterior aspect of the neck. Additionally, because tackles from behind the Ball-carrier often occur when the players are travelling at higher speed, the involvement of other factors cannot be ruled out. An analysis of match tackling technique evaluating tackle direction may be useful in clarifying its role in injury aetiology and informing interventions to train players to make and receive tackles from any direction safely.

59 3.4.4.4 Speed

Game speed, or player speed during a match, has been presented as a cause of injury in other sports, such as Australian rules football (Norton, et al., 2001). Higher player velocities result in higher impact energy and collision injuries have been associated with serious and catastrophic injuries in several sports (Boden, 2005; Orchard, et al., 2002). Player speed prior to impact will also affect impact magnitude and the player’s ability to react to perturbations. In rugby, the approach speed of the Ball-carrier and Tacklers has been postulated as a risk factor for injury based on the observation that positions with a greater exposure to open play had a higher incidence of injury (Roux, Goedeke, Visser, van Zyl, & Noakes, 1987) and has been accepted by several authors (e.g. Garraway & Macleod, 1995; D. C. Hughes & Fricker, 1994). Match speed has also been proposed as a potential risk factor for knee injuries (Dallalana, et al., 2007) and a cause of increased injury rates following professionalism in 1995 (Bathgate, et al., 2002).

The speed of players leading into the tackle has been investigated in two studies. In their case control study of tackling injuries, Garraway et al. (1999) evaluated player speed using a scale from one (least speed) to five (highest speed). They found that 44% of injuries occurred in tackles where both players were travelling at maximum speed prior to impact. Thirty five percent (35%) of injuries occurred in situations where one player was stationary or moving significantly slower than the other player. Within these tackles, the player with the lower velocity was mainly injured (n= 20/25). Wilson et al. (1999) used a categorical method to evaluate player velocity from video of tackle injuries. They described player movement based on whether the player was jumping, running or walking, diving or falling or stationary. They found that in seventy percent (70%) of injuries the player was moving. A lower proportion of injuries are reported in circumstances where either the Tackler or the Ball-carrier was stationary (30%).

It is widely accepted that traumatic injury is caused by energy transfer above the level that bodily structures can tolerate. Higher player velocity results in higher amounts of energy that must be dissipated, increasing injury risk. However, rugby

60 is a dynamic game and players are commonly running at the time of tackle contacts that do not result in injury. Based on the information in the literature, an analysis of the tackle situation should evaluate the speed of all players involved in events that do and do not result in injury.

3.4.4.5 Tackler engagement and tackle type

Tackler engagement refers to the number of Tacklers involved in a tackle and the sequence of their engagement. Tackles involving multiple Tacklers have been discussed earlier as a risk factor for cervical injury based on the findings of several authors (Browne, 2006; Carmody, et al., 2005; Scher, 1983a). Injuries occurring through multiple player tackles have not been addressed by prospective injury surveillance studies. Only one study describes tackle injuries arising from general play according to the number of players involved. That study found that one in every five tackle injuries involved multiple players (Garraway, et al., 1999).

Similarly, the sequence of engagement of Tacklers with the Ball-carrier in the tackle has not been identified specifically in the literature as an injury risk in rugby union. However, Wilson et al. (1999) observed that injuries to stationary players often occurred when a player was held in a tackle and then experienced a secondary impact. In a multiple Tackler situation, an opponent entering a tackle while the Ball-carrier is held could contribute to an injury by applying an external force when the Ball-carriers mechanisms of maintaining stability or range of motion are hampered. The player may also be unaware of the additional Tackler. At the time this research was conducted, there had been no research investigating the frequency of tackles involving more than one Tackler or examining the sequence of Tackler impact and its effect on injury risk.

Tackle type has been used to describe general tackling technique employed by the Tackler. Tackle type has been poorly defined in the literature and the frequency of execution of tackles by tackle type has not been investigated. The study of Wilson et al. (1999) enumerated 5 tackle types (Smother, Stopping, Shoulder charge, Trip and Other (Scrag)) but did not provide a detailed definition of the tackles. The

61 majority of tackle injuries were associated with stopping tackles (57%) where the ball was “available to be played in the tackle”. The authors described Shoulder charge and Other (Scrag) tackles as illegal. Garraway et al. (1999) identified three types of tackles (Classical, Smother and Big hit), but again these were not defined. In terms of injury association, 18% of tackle events were described as ‘Smother’ tackles. These findings are valuable in describing injury situations though they cannot be confirmed as injury risk factors because the level of exposure to these types of tackle is not known. This has been highlighted as an area of study for further investigation (Wilson, et al., 1999).

Other authors have made recommendations based on their observations, such as for the Tackler to keep their head up and place their head to the side of the target while grasping the pelvis with both arms (Scher, 1978). This observation is supported by coaching material which, while also not identifying specific tackle types, promotes the shoulder as the first point of contact in preference to the arm (ARU, 2006a; NZRU & ACC, 2005a) as the preferred method of tackling.

3.4.4.6 Collision with the ground and other players

Players involved in the tackle are subjected to extrinsic forces arising from the impact between a Ball-carrier and an opponent. Aside from the primary player on player collision, a further collision can occur when the Tackler falls to the ground. The proportion of injuries arising from ground contact is lower than injuries attributed to the tackle contact. However, player contact with the ground is a common outcome of the tackle for both the Ball-carrier and the Tackler. In their video analysis of tackle injuries, Wilson et al. (1999) observed that almost two thirds of injuries occurred during the tackle impact while one fifth occurred during ground contact. However, anecdotal evidence suggests that the severity of ground contact injuries may be higher. Several authors have made observations based on empirical evidence. Archibald (1962) described that fractures and dislocations usually arose from tackling incidents where the injured player fell awkwardly underneath another player. Garraway et al. (1999) found that all shoulder dislocations (n=12) occurred when a player fell to the ground and landed on this

62 body part. Davidson (1987) observed a higher occurrence of clavicular fractures during one particular season out of several studied and associated this with harder ground conditions. This view was supported by Sparks (1981) who stated that hard grounds predisposed players to upper limb fractures. The study by Wilson et al. (1999) also found that when players fell to ground the landing was most often associated with injury.

The mechanism of shoulder dislocation has been presented earlier in this thesis as a fall to the point of the shoulder or axial loading of the upper limb. However, it should be noted that the mean centre of pressure recorded by Trewartha and Stokes (2003) during the tackle impact, one centimetre lateral of the acromion, does not preclude AC joint injuries as a result of the tackle impact. As has been previously stated, high velocity tackles are associated with a higher peak impact force than ‘slow’ tackles. Two studies of the tackle have attempted to describe the magnitude of the tackle impact force and the circumstances of the player going to ground. Garraway et al. (1999) used a scalar method (between one and five) to describe the impact and analyst’s impression of the magnitude of the tackle force. The proportion of tackles that were described as forceful which resulted in an injury was not presented but the authors did find that forceful tackles originated mainly from in front of the Ball-carrier when the Tackler had more time to set themselves. Wilson et al (1999) used a categorical method to describe the tackle impact and attempts by the Ball-carrier to moderate the effects. They found that the actions of ‘going with the impact’ or ‘turning in the tackle’ seemed to be less associated with injury.

When discussing methods to prevent tackle injury in rugby league, Raftery et al. (1999) proposed that players should be coached to fall safely and similar recommendations have been made for rugby union (Addley & Farren, 1988). Evaluating the ground impact and enumerating specific factors of the contact that may result in injury, such as axial loading and head contact, could assist in developing evidence based coaching interventions to improve skill execution and reduce injury.

63 3.4.4.7 Field position

The epidemiological literature specific to rugby has not investigated field position and only one study of injury in the tackle had used it to describe injury in rugby union when this research commenced. In their study of tackle injuries, Garraway et al. (1999) divided the field using a grid with squares of five metres and both players (the Tackler and Ball-carrier involved in the injury event) were asked to nominate their field position at the time of injury at the completion of the match. Figure 3.3 is from the study and shows that injuries were generally evenly spread across the field. However, the authors highlighted injuries occurring to players attacking their opponent’s goal line, noting that thirty six percent (36%) of injury episodes occurred within the two 22 metre zones of the field. During personal communication with coaches it has been postulated that players may accept a higher risk of injury in order to score points or to prevent the opposition from scoring.

Only one other study that was retrieved using the search terms presented in Chapter Three reported field position and injury. Andersen, Tenga, Engebretsen and Bahr (2004) evaluated video of events where the match was stopped for injury using Football Incident Analysis (FIA) (Andersen, et al., 2003). FIA evaluates position on the field according to a grid formed by dividing the field into thirds lengthwise (defending, midfield and attacking) and across the field (sideline, midfield, sideline). Their results supported the findings of Garraway et al. (1999) that a higher proportion of injuries occurred in the attacking and defending zones of the field. They also observed a higher proportion of ‘incidents’ (defined as events where play was stopped for an assumed injury) in this part of the field.

A search of the Medline database was conducted to identify research in other sports using the key words “Field”, “Position”, “Sport” and “injury”. The search returned 27 articles. The majority of articles retrieved were not specific to the position on the field at the time of injury. Subsequent to the development of the protocol four studies have used field position to describe tackle injuries. Three of these studies have used the analysis method developed in this research (Fuller, et al., 2010; Fuller, Brooks, et al., 2007; McIntosh, Savage, et al., 2010).

64

Figure removed due to copyright restrictions

Figure 3.3: Position of all injuries recorded in Garraway et al. (1999; n=72) superimposed on the field of play. Squares represent the home team, circle represent the away team.

3.4.4.8 Muscle Damage

Two studies have measured the concentration of biomarkers of muscle damage associated with participation in a rugby match. The studies used elevated concentrations of serum creatine kinase to indicate muscle damage, and attributed it to collisions with other players and repeated eccentric muscle contractions associated with intermittent running and/or sprinting. Forwards perform a higher number of tasks involving collisions in a game (International Rugby Board, 2005a). These activities cause damage to the muscle and result in a reduction in force production capabilities. It is hypothesised that the protective role of the muscle in preventing hyperextension and movements beyond the range of motion is diminished as a result (Smart, Gill, Beaven, Cook, & Blazevich, 2008; Takarada, 2003). Enumerating the number of tackles that an individual player executes in each match could provide evidence to support this.

65 3.4.4.9 Skills level and skill training

The utilisation of a program instructing correct technique for both the Ball-carrier and the Tackler is a logical step towards a reduction in injuries and has been suggested in several studies (Scher, 1978; Wilson, et al., 1999). The governing bodies of rugby union in Australia and New Zealand have developed programs that instruct participants on the safe execution of skills in a number of facets of the game (ARU, 2006a; NZRU & ACC, 2005a). A first step in developing programs addressing technique deficiencies lies in identifying the aspects of technique that are representative of tackles performed in matches in the competition of interest, and those aspects which are associated with injury. It is difficult to evaluate a player’s training from video, though general inferences regarding level of skill could be drawn according to level of play and grade.

3.4.4.10 Level of play and playing position

The incidence of injury when tackling and being tackled have been discussed earlier and are presented in Table 3.5 by level of play. In summary, the general trend at all levels is for a higher observed proportion of injuries affecting the Ball- carrier (Brooks, et al., 2005c; Durie & Munroe, 2000; McIntosh, et al., 2008), although one study has produced contrary findings (Best, et al., 2005). Differences in skill execution, especially for the Tackler, have been identified as a risk factor for injury by several authors and the association between level of play and injury aetiology requires further investigation (Clark, et al., 1990; Silver & Gill, 1988). Such an investigation should investigate changes in the characteristics of tackle execution/technique according to level of play. General injury trends for playing position were reviewed in section 3.3.2.5. and the absence of a representative pattern of injury by playing position was noted. Differences in the reported injury data indicate that trends are specific to level of play and geographical region. Such variability may also suggest that seasonal injury incidence by playing position may also vary. Investigation of the tackle to establish the characteristics of technique and injury would assist in monitoring changes in injury patterns and identification of injury risks for each playing position.

66 3.4.4.11 Weather, field conditions and other factors

The relationship between weather and field conditions and rugby union injury was discussed in section 3.3.5. A common perception is that harder grounds lead to higher injury rates, especially to the upper limb (Alsop, et al., 2005; Davidson, 1987). However, there is disagreement over the influence of weather and field conditions on injury aetiology and, to date, only one attempt has been made to investigate the role of pitch and weather conditions in injury aetiology objectively. This study was released after the analysis protocol had been developed (Takemura, et al., 2007). Further, weather conditions may contribute to tackle injury aetiology through their effect on surface conditions and player fatigue. Weather conditions have a direct influence on surface friction, an important component of stability (Elliott & Wood, 1995). It is conceivable that lower surface friction can influence the number of tackles and their impact characteristics, resulting in modifications to technique. They may, therefore, influence injury risk (Alsop, et al., 2005; Lee & Garraway, 2000; Orchard, 2002).

3.4.5 Summary and Difficulties in Analysing the Tackle

This chapter has reviewed the injury aetiology and injury risks factors identified for the tackle in epidemiological and other research. At the time that this research commenced there was no published research describing video analysis of injury in the tackle in rugby. One group had enumerated the phases of play from matches within the sample population in which they were conducting an injury surveillance study. From this they inferred some associations, but injury incidence was not reported per event and it was not clear if they were able to successfully link injury data with corresponding video of the event (Fuller, Brooks, et al., 2007). Another group had described ‘medical’ events where a match was stopped for a player to receive medical aid, but these were not confirmed injuries (Wilson, et al., 1999).

There are several factors which make the analysis of the tackle difficult. Tackle injuries do not affect a specific population, for example, males versus females, or schoolboys compared to elite players. Tackle injuries have been determined as

67 ‘whole sport’ or ‘global’ injury problem. (McIntosh, et al., 2008). Experimental design allows many intrinsic risk factors to be separated as independent variables, allowing for assessment through quantitative methods. However, like many other sporting skills, the tackle is a multi-factorial event. Given the large number of factors which may contribute to injury aetiology and the potential inter- relationships between these factors and injury, a valid quantitative analysis of the tackle to determine injury aetiology may be difficult to conduct. The following section will review the analysis frameworks available for assessing human movement.

3.5 Analysing Human Movement

Chapter Two emphasised the importance of identifying injury risk factors to develop successful injury prevention programs. Section 3.4 identified a number of proposed injury risk factors, both intrinsic and extrinsic, but in most cases it is unclear how often these are present in injury situations and how several risk factors may interact to cause injury. In their review of epidemiological methods for sports science, Walter and Hart (1990) delineate between identifying risk factors and biomechanical analysis as distinct steps, with biomechanical investigation following the identification of risk factors. That is not to say that biomechanics does not play a role in identifying risk factors through evaluating aetiology. Currently, our understanding of the tackle is limited to a description as a multi-factorial collision between a Ball-carrier and one or more Tacklers. While a particular tackle technique is advocated, utilisation of that technique during a match has not been evaluated. Bahr and Krosshaug (2005) propose that a description of injury events should incorporate:

x Playing situation x Athlete opponent behaviour x Whole body biomechanical description x Joint/tissue description

68 While the playing situation has been described, to some degree, through event frequency analyses and identification of the event associated with injury, the description of the tackle requires greater focus on information from these other perspectives. A method to evaluate the tackle, capable of describing skill execution and injury risk factors from a whole body biomechanical perspective and, where appropriate, a local joint perspective is required.

Biomechanics is the study of the effect of movement and loads applied to the body through the application of mechanical principles. The discipline is concerned with the relationship between these loads and injury, performance and functionality (Marshall & Elliott, 1995). Biomechanics is commonly applied in coaching and clinical settings to investigate skills and develop such an understanding. The analysis of movement for the purpose of evaluating and improving performance is called technique analysis (Lees, 2002). There are a number of research frameworks which may be applied depending on the scope of the research, the type of skill to be investigated (open/closed) and the suitability of the performance environment to direct enquiry. These will be discussed further in this section.

Biomechanical research of rugby union skills has been limited. Since 2008, three biomechanical studies have been published targeting the line out and the tackle (Pain, et al., 2008; Trewartha, Casanova, & Wilson, 2008; Usman, et al., 2011). At the time that this research commenced, however, the scrum had been the primary target of the few investigations that had been conducted (Milburn, 1990, 1993; Quarrie & Wilson, 2000) and only one study had evaluated the kinetics of tackling (Trewartha & Stokes, 2003). There are considerable differences between the tackle and scrum from a skill acquisition perspective. The scrum is a largely static skill and scrummaging practice is often performed under closed conditions with a static “scrum machine”. The tackle has been previously described as a skill occurring in a dynamic environment (section 3.4). The research of Milburn, and Quarrie and Wilson resulted in changes to the rules of scrum engagement and the introduction of the Under 19 scrum Law forbidding pushing at engagement. Only one other investigation of rugby skills has been conducted, a kinematic evaluation

69 of the effect of ball carrying method on sprint speed (Grant et al., 2003). Both of these skills can be replicated under closed conditions in the laboratory.

Another method of investigating movement patterns, albeit to evaluate physiological demands, is time motion analysis. Several studies have used this method to quantify player movement during a rugby match (Deutsch, Maw, Jenkins, & Reaburn, 1998; Docherty, Wenger, & Neary, 1988; Duthie, Pyne, & Hooper, 2005; McLean, 1992). These studies have estimated the physiological demands by calculating the distances travelled and the frequency of player involvement in match events using video methods or global positioning systems. The results have confirmed that while backs cover greater distances during a match, forwards are involved in more contact events (Deutsch, et al., 1998; International Rugby Board, 2005a). Time motion analysis can enumerate event frequency and duration at a match and individual level, but the results are unable to contribute to our understanding of tackling skills.

The aim of this section of the literature review is to consider the biomechanical frameworks available for technique analysis, provide justification for selecting the qualitative framework for investigating the tackle over others, and to identify tools that may be used to develop a qualitative analysis protocol. In section 3.5.1 the analysis frameworks will be broadly defined and the strengths and weaknesses and typical research applications will be presented. Sections 3.5.2 to 3.5.4 will review the advantages of qualitative methods for developing hypotheses, present models for qualitative analysis of sport skills and address methods for limiting bias in qualitative analysis. The final parts of this section (3.5.5 to 3.7) will focus on practical applications of qualitative analysis for movement evaluation. Examples of qualitative research in sporting, clinical and occupational settings will be reviewed and statistical methods for assessing reliability of qualitative data will be presented.

70 3.5.1 An Overview of Research Frameworks for Technique Analysis

The methods used for technique analysis can be broadly assigned to three analysis frameworks. Hay and Reid (1988) identified quantitative analysis and qualitative analysis as frameworks for the analysis of human movement. With the recent development of simulation, optimisation and other predictive and generally computer based methods, predictive analysis has been added to the two existing methods (Marshall & Elliott, 1995). Each of the three frameworks has advantages and disadvantages for technique analysis.

3.5.1.1 Quantitative analysis

Quantitative, or objective, methods are defined as those that provide a description or assessment of a movement or phenomena in numerical terms (Hamill & Knutzen, 1995; Kreighbaum & Barthels, 1996; Lees, 2002; Powers & Harrison, 1999). Data are usually collected using instrumented data collection techniques and stored for further analysis. Examples of quantitative analysis are kinematic analyses from cinematography, kinetic analysis and electromyography (EMG). Quantitative analysis is considered the preferred method for biomechanical investigations of human movement (Hamill & Knutzen, 1995; Hay & Reid, 1988). Biomechanists are most interested in principles that create or moderate movement, parameters such as force, torque, displacement, velocity, acceleration and trajectory (Bartlett, 2008; Hamill & Knutzen, 1995; Hay & Reid, 1988). Changes in these parameters can be too small and occur too rapidly to be observed in real time with unassisted (qualitative) observation methods.

Quantitative analysis provides a rigorous, repeatable and high validity method for the numerical measurement of these factors, allowing for objective comparison of a movement or skill. As a result, data can be aggregated and analysed statistically to determine levels of significance of any differences between subjects and trials. A further advantage of quantitative methods relates to the storage of data. Marshall and Elliott (1995) identified the collection of a permanent record of a number of

71 trials which can be analysed and viewed later as an important component of quantitative analysis. Storing the record allows for repeat analysis of the data at a later stage, e.g. if the statistical method is revised or if an error in data processing is identified.

Quantitative analysis is a powerful evaluative tool for studies of human movement. However, it cannot be applied successfully to all problems. Sofaer (1999) stated that the ability to measure (a movement) quantitatively relies on a thorough understanding or conceptualisation (of the movement). Quantitative analysis techniques are best used for the investigation of closed skills and human movement is often complex and dynamic (M. D. Hughes & Bartlett, 2002). The dynamic nature of the skill and environment mean that movement is influenced by intrinsic variables, such as skill level, and extrinsic variables, such as the interaction between that athlete being studied and their opponent (Andersen, et al., 2003; Hall, 2006; Patton, 2002). The result is that quantitative methods cannot be applied to all cases because the problem cannot be reduced to produce a numerical solution. The main method used to address movement complexity in quantitative analysis is to limit the number of variables studied by simplifying movement patterns or components of the movement (Thomas, Nelson, & Silverman, 2005).

Additionally, quantitative analysis requires expensive, specialised, equipment requiring specialist training and data collection and processing may be time consuming. It is not always possible to apply quantitative methods to a movement. For example marker based motion analysis of the tackle would not be possible because of difficulty maintaining marker location during contact with an opponent and marker obstruction. Further, because equipment used to collect data is specialised, quantitative analysis is normally restricted to the laboratory (Hay & Reid, 1988). The variable temporospatial nature of many game situations as opponents move in response to each other’s actions generally cannot be reproduced within the laboratory setting. Additionally, open skills that are investigated under closed conditions in the experimental setting can be heavily restricted to the point of simplification, limiting generalisations that can be made from the results. While

72 recent technological advances have resulted in wearable devices, which can be applied to measure kinetics and kinematics, on the field application of these devices is limited because of specialised construction, athlete resistance to in-game use or data storage limitations among other things.

A further difficulty is that quantitative methods can generally not be applied retrospectively and this limits their application to situations when an injury is known to have occurred. To be valid, a kinematic analysis, for example, must be performed in a scaled space from stationary camera perspectives and it is very difficult to obtain such conditions from sports telecasts. Additionally, for this method of analysis, the absence of force data makes it impossible to accurately estimate the load causing the injury. Quantitative frameworks have been used to investigate injury situations when they occur unexpectedly during laboratory testing (Barone, Senner, & Schaff, 1999; Krosshaug, et al., 2005; Zernicke, Garhammer, & Jobe, 1977). However, research intended to cause injury cannot be conducted because of the obvious ethical issues associated with causing injury and harm to participants as the aim, or a likely outcome, of research.

3.5.1.2 Qualitative analysis

A qualitative or subjective framework is defined as the collection and analysis of data through subjective, non-numerical processes (Kreighbaum & Barthels, 1996; Whitley & Crawford, 2005). Qualitative frameworks are commonly used in human movement science, for both athletic and clinical applications. They are also used in a number of other disciplines including psychology, health science and social science. Hay (1993) wrote that the study of any field begins with an attempt to obtain a global understanding about the content of the field and qualitative methods have been identified by several authors as useful for preliminary investigations where little is known about a skill or area of study. Sofaer (1999) proposed qualitative analysis was most suited to developing an understanding about complex phenomena because of its flexibility. This view was supported by Patton (1999), who believed that qualitative analysis was justified when the research questions are

73 related to the description and understanding of a particular event about which little is known or that occurs in a dynamic environment.

The flexibility of qualitative frameworks arise from data collection techniques that can include observation, interviews, questionnaires and discussions (Greenfield, Greene, & Johanson, 2007; Sofaer, 1999). A result of the flexibility of these methods is that they can be applied in different research settings without significant specialist training or equipment. For example, observation is recognised as a useful tool for the analysis of human movement and it is widely promoted for technique remediation in coaching (Hamill & Knutzen, 1995; Knudson & Morrison, 2002). With sufficient knowledge of the activity and the concepts pertinent to the movement (e.g. anatomical and mechanical) the analyst can appraise performance and provide instantaneous feedback in coaching and teaching situations (Arend & Higgins, 1976; Hay & Reid, 1988; Knudson & Morrison, 2002). An observational analysis can be applied either during a face to face coaching session with an athlete or, alternatively, it can be retrospectively applied to video of movement skills and injury events meaning that data can be collected under natural conditions.

The main perceived flaw of qualitative analysis is bias associated with the subjective nature of data collection. This judgment stems from the heavy dependence that qualitative methods have upon the experience and perspective of the researcher (Sofaer, 1999) and limitations of perceiving differences in dynamic movements in real time (Knudson, 1999). Scientific enquiry generally emphasises objectivity and perceived bias in qualitative methods has resulted in questions about its accuracy and reliability (Patton, 2002). Biomechanical evaluations are generally heavily reliant upon numerical measurement. Research requiring observers to estimate the magnitude of kinematic variables have found the results to be both unreliable and inaccurate (e.g. Krosshaug et al., 2007). An outcome of these findings may be that qualitative frameworks are not considered as a preferred method for research. In fact, several biomechanics texts mention qualitative analysis only in the context of coaching and teaching (Hall, 2006; Hamill & Knutzen, 1995; Hay & Reid, 1988). However, there is consensus amongst several

74 authors that the reliability issues associated with qualitative analysis can be overcome through careful planning and preparation for the research (Arend & Higgins, 1976; Knudson & Morrison, 2002; Patton, 1999; Sofaer, 1999).

3.5.1.3 Predictive analysis

The third framework, predictive analysis, uses simulations and human body models to describe movement performance. Predictive analysis can assist in evaluating complex movement skills or investigating optimal performance criteria. Movement may be described through simple, single input, models, such as spring-damper systems, or more complex representations of the human body (Lees, 2002). Predictive methods can be used to investigate hypothetical scenarios by manipulating input parameters and limiting movement inconsistency, through controlling fatigue and technique variability, to determine the effect of minor adjustments of technique on performance (Marshall & Elliott, 1995). They are also useful for investigating phenomena that would otherwise be difficult to evaluate, such as in vivo joint kinetics and kinematics and tissue strain (eg. Lloyd & Besier, 2003; Viano et al., 2005). At the time that this research commenced they had been used to investigate concussion in soccer and American football and they have recently been used in rugby union and Australian rules football (Fréchède & McIntosh, 2009; Pellman, Viano, Tucker, Casson, & Waeckerle, 2003; Shewchenko, Withnall, Keown, Gittens, & Dvorak, 2005).

The disadvantages of the predictive framework result from their level of complexity. Simple models may result in over simplification of the movement to the extent that it becomes unrealistic or relevant only for specific situations. Complex models may be time consuming to develop, costly and require increased computer resources with increased sophistication. Their reliability heavily depends on their state and level of validation, a phase that is increasingly complex with the level of detail and of information provided by the model (Krosshaug, et al., 2005).

75 3.5.2 Selecting a framework for analysis of the tackle

“If we ignore the things that we cannot measure, then we cannot fully understand what we are researching.” (Sofaer, 1999)

The choice of framework for an investigation is dependent upon the research question and the object evaluated. The scrum has been highlighted earlier in this thesis as a rugby specific example where the injury prevention paradigm of van Mechelen and colleagues (1992) was followed full circle (section 2.1). However, scrum engagement occurs under conditions that are more controlled than the tackle. This makes the scrum, particularly individual performance or the combined performance of the front row, more suitable for quantitative technique analysis (M. D. Hughes & Bartlett, 2002). Considering the requirements, strengths and weaknesses of the respective methods, it is clear that none of the three frameworks can be successfully applied in all research situations and that qualitative and predictive methods are not suitable at this stage for investigating the tackle for the purpose of developing an understanding of skill execution and injury risk.

There is a clear correlation between the breadth of the target and the type of research framework used in an investigation and it is common that there is some overlap of research frameworks within a research protocol (Knudson & Morrison, 2002). Sofaer (1999) argued that a thorough understanding of a target activity is developed through a staged investigative approach utilising several research methodologies. Krosshaug et al. (2005) suggested that using a number of research approaches improved the validity and accuracy of the research. Such an approach results in a gradual reduction in the number of questions and uncertainty over time as factors related to movement performance are identified, measurement methods are developed and the focus of research questions narrow (Sofaer, 1999). Flexibility was identified in the preceding section as the primary strength of qualitative frameworks. Qualitative methods are commonly used to describe and explain phenomena accurately to reflect their performance in context, i.e. how they occur in the ‘real world’ (Patton, 2002).

76 When performed systematically, a qualitative analysis presents a description of events based on selected criteria. As a result, it can provide perspective and context for specific behaviours (Greenfield, et al., 2007). The occurrence of the targeted criteria or phenomena can be recorded and statistically aggregated to determine injury trends, technique adoption and inform future research. The result is an understanding of the context in which the event occurs and other factors, such as the performance environment, which may be influencing the movement. This allows dependent relationships (e.g. injury aetiology or performance enhancement) to be identified and hypotheses to be refined for subsequent investigations using quantitative analysis (Sofaer, 1999). A key concept that is emphasised in the literature is the systematic nature of effective qualitative techniques. A systematic approach, applied to the preparation, evaluation and intervention results in improved accuracy and reliability of qualitative research frameworks. The methods for preparing a systematic analysis will be reviewed in the next section.

3.5.3 The Qualitative Analysis Process – Attaining Objectivity and Addressing Bias of Subjective Analysis

Qualitative analysis has been defined earlier in this chapter as the collection of data through subjective or non-numerical processes. This definition does not provide any guidance as to how the limitations of qualitative methods that have been identified may be addressed. In order to develop an understanding of the qualitative analysis process it is important to develop a definition that is specific to technique analysis. The definition provided by Knudson and Morrison (1996) is representative of definitions used by several authors in biomechanics texts (e.g. Hall, 2006; Hamill & Knutzen, 1995). They define qualitative analysis as:

“The systematic observation and introspective judgement of the quality of human movement for the purpose of providing the most appropriate intervention to human performance.” (definition one)

Two aspects of definition one are noteworthy. Firstly, the use of the term observation and the reference to intervening in performance may evidence support

77 of the preconception expressed by several authors that qualitative analysis is primarily a coaching tool (Arend & Higgins, 1976; Hall, 2006; Hamill & Knutzen, 1995; Hay & Reid, 1988). However, Patton (2002) identified the importance of observation as a data collection tool in qualitative inquiry, and the recurring inclusion of observation in the definitions of qualitative analysis reinforced the importance of the method in movement evaluation. On the other hand, observation is an exemplar of the means by which doubts arise about the qualitative framework. The second aspect of definition one that is of interest is its emphasis upon conducting a systematic qualitative analysis through observation (or data collection) and judgement (or evaluation). In other words, there must be processes for collecting information and evaluating the information collected. However, definition one makes no mention of preparation and this process is better represented in the definition of Hay and Reid (1988), who expand on the notion of a systematic analysis by inferring preparation as an important aspect of qualitative analysis of human movement:

(In its complete form the method consists of) “a systematic evaluation of not only the result but also of the various factors that have contributed to the result.” (definition two)

The process of identifying the factors that contribute to the result could be considered as synonymous with the preparative phase. These two aspects that have been identified, observation and the systematic nature of the analysis are important for a successful qualitative analysis.

Qualitative analysis relies heavily on the perspective, experience and preparation of the investigator (or observer) and reliability is influenced by this dependence. In qualitative frameworks the investigator is the data collection instrument (Patton, 2002; Thomas, et al., 2005) and the amount of data that can be captured through observation is substantial (Liebermann & Franks, 2008). Observation allows the researcher to scrutinise player behaviour and interaction with, or response to, their environment, enabling evaluation of skill performance and feedback for improvement (Hay & Reid, 1988; Knudson & Morrison, 2002; Payton, 2007).

78 However, it is because of reliance upon the investigators’ judgement and experience that there are doubts about the reliability and accuracy of qualitative methods (Thomas, et al., 2005). For example, estimating the magnitude of joint angles is difficult even for experienced clinicians (Krosshaug, et al., 2007) and error may be introduced through qualitative components of largely quantitative analysis, such as marker placement in clinical gait analysis (Noonan et al., 2003; Schwartz, Trost, & Wervey, 2004). Other research demonstrates that experience does not result in an improvement when perceiving differences in performers (Franks, 1993; Knudson, 1999). Doubts about the accuracy of qualitative analysis are summarised by Maslovat & Franks (2008; page 3):

“Traditional coaching intervention often involves subjective observation and conclusions based on a coach’s perceptions, biases and own previous experiences. However, a number of studies have revealed that subjective observations are potentially both unreliable and inaccurate”

Additional limitations, such as remembering and recalling all of the information that has been observed and errors associated with observation in real time or from only one perspective have also been identified (Hay & Reid, 1988). Some of these concerns about unreliability and inaccuracy of qualitative motion analysis can be partially addressed through simple measures such as the use of video and frame by frame playback or slow motion replay (Knudson & Morrison, 2002). A more complete method of addressing inaccuracy and unreliability is through developing a systematic analysis protocol (Arend & Higgins, 1976; Hall, 2006; Hay & Reid, 1988; Knudson & Morrison, 2002; Marshall & Elliott, 1995). This process is described by Patton (2002) who wrote that to widen acceptance as an appropriate method for scientific investigation, qualitative analysis must increase its legitimacy and credibility by emphasising traditional scientific principles of objectivity.

The notion of conducting a subjective investigation objectively appears contradictive upon the first encounter. However, within qualitative analysis, objectivity does not refer to numerical measurement but to reproducibility. Patton (2002) presented several criteria for conducting subjective inquiry within what he

79 calls scientific tradition to emphasise objectivity and minimise investigator bias (Figure 3.4). It is here that the importance of ‘preparation’ in definition two becomes clearer. The systematic planning and preparation of a qualitative analysis will contribute significantly to reducing the weaknesses of the method such as investigator bias by developing reliability and validity (Arend & Higgins, 1976; Hall, 2006; Hay & Reid, 1988; Knudson & Morrison, 2002). In summary, Patton (1999) recommends that the method must apply multiple coders in analysis and report the inter-rater reliability to establish the validity and reliability of the analysis method. The strength of the analysis will be increased if multiple questions addressing an aspect correlate to confirm an observation (triangulation) (Patton, 1999, 2002).

Traditional scientific research criteria

Objectivity of the inquirer Validity of the data Systematic rigor of fieldwork procedures Triangulation (consistency of findings across methods and data sources) Reliability of codings Correspondence of findings to reality Generalisability (external validity) Strength of evidence supporting casual hypotheses Contributions to theory

Figure 3.4: Criteria for qualitative analysis from a scientific perspective (Patton, 2002; p 544)

An existing framework from which a qualitative analysis method may be developed through traditional scientific principles is the ‘systematic method’ that has been proposed by several authors to improve the accuracy of qualitative analysis (Arend & Higgins, 1976; Hay & Reid, 1988; McPherson, 1996). The model follows basic scientific investigative principles (preparation, data collection, evaluation, outcomes) and the ‘systematic’ process incorporates four important steps:

80 1. Development/preparation of a model showing the relationships between the result and the factors that produce that result. 2. Observation of the performance and identification of faults. 3. Evaluation of the relative importance of these faults. 4. Instruction of the performer in accord with the conclusions reached in the course of the analysis.

These steps provide a framework for the systematic development of an analysis protocol, and for the collection and evaluation of data using qualitative methods. They were summarised visually in the integrated model of qualitative technique analysis presented by Knudson and Morrison (Figure 3.5). For the purpose of developing the protocol the first three steps are relevant, however the model is clearly specific to the conduct of qualitative analysis and does not assist in selecting attributes for a qualitative analysis.

Figure removed due to copyright restrictions

Figure 3.5: Integrated model of qualitative analysis (Knudson and Morrison, 2002)

81 Knudson (2000) stated that the validity and reliability of qualitative analysis is improved through the careful development of an appropriate protocol incorporating clear definitions and simple evaluation methods. Definitions of what is to be analysed and how, assists the observer to identify what they are looking for (Arend & Higgins, 1976). The methods used to evaluate the attributes or characteristics of a target are dependent upon the criteria selected for the analysis and this, in turn, is dependent on the preparation of the analysis and on the experience and opinions of the researcher (Knudson & Morrison, 2002; Kreighbaum & Barthels, 1996). An encompassing framework for this process does not exist, but several authors have presented models which may assist in preparing a qualitative analysis protocol.

3.5.4 Models for Preparing a Qualitative Analysis Protocol

The staged process for qualitative technique analysis starts with the preparation or development of the qualitative analysis method (Figure 3.5). Hay and Reid (1988) state that a successful qualitative analysis requires an understanding of the skill to be analysed and the sport from which it is derived. A basic analysis of any skill requires knowledge of the movement goal and any sport specific constraints, such as the rules or laws, as a minimum. For example, in rugby union a tackled player who is falling to the ground may be expected to act to prevent injury. However, the match constraints of maintaining possession of the ball during the fall and contorting to present the ball to their own defensive half place additional constraints upon the task. A comprehensive frame work for the development of an analysis method does not currently exist but several authors have presented models of the analysis process, including Arend and Higgins (1976), McPherson (1996) and Knudson (2000). Methods that may be useful when organising key variables and critical features of technique have also been presented, including those by Hay and Reid (1988) and by Haddon (1999), who presented his model from the perspective of determining aetiology from a description of the event.

The earliest model identified in the literature search that was conducted for this research (section 3.1) was developed by Arend and Higgins (1976) (Figure 3.6).

82 Figure removed due to copyright restrictions

Figure 3.6: A strategy for the subjective analysis and observation of human movement (Arend & Higgins, 1976)

83 Their model was the first to present a staged approach to qualitative technique analysis, dividing the analysis into the same steps as the ‘staged process’ presented in Figure 3.5 (planning/pre-observation; data collection/observation and evaluation/ post-observation). The first phase attempts to develop an understanding of the movement through understanding principles of skill acquisition and environmental and movement constraints. The second stage applies the understanding developed in the first phase to the movement while the third phase evaluates the movement based on the protocol and determines the necessary feedback to improve performance.

Arend and Higgins (1976) suggest that after identifying the goal of the movement, an understanding of the movement can be developed by identifying the critical features of technique. Also known as key performance points, the authors define the critical features of technique as those aspects of the movement or skill which can be least modified to achieve the primary goal of the movement. However, the authors do not present a rigorous framework for identifying critical features of technique. While they suggest that the features can be identified through the initial stages of their model (Figure 3.6), the authors acknowledge that such a process takes much practice and experience to be successful. The difficulty arises, therefore, in not introducing additional sources of error or bias while relying on the experience and perspective of an individual when identifying these features.

Hay and Reid (1988) presented a model which may be useful for identifying the critical features of technique (Figure 3.7). The model, known as the deterministic or hierarchical model, evaluates the movement by identifying the primary movement goal and determining the features of movement that contribute to achieving that goal. For example, for discus throwing, the final displacement of the discus from the thrower is the result, the angle and velocity of release are the primary determinants of the result and other factors, such as whole body angular acceleration and limb length, contribute to these determinants. It can be quite complex to determine what is the cause and what is the effect in some cases and this method may assist to determine the biomechanical factors that contribute to skilled performance.

84

Figure removed due to copyright restrictions

Figure 3.7: The deterministic or hierarchical analysis model (Hay & Reid, 1988)

Another of the models for qualitative technique analysis was developed by McPherson (1996) (Figure 3.8). Like the model of Arend and Higgins (1976), it is also divided into similar phases to those identified in the ‘staged process’ of qualitative analysis. Only the first phase is relevant to the development of an analysis protocol. McPherson’s model identifies evaluating the purpose of the movement as an important aspect for developing an analysis protocol. The model incorporates the identification of mechanical variables and critical features of technique (as described in earlier models) within the process. The model then builds on earlier models by introducing a new aspect of planning the data collection. This may represent considering the optimal position to observe the skill, the number of camera views used or the timing that the focus of an analysis is shifted between different aspects of the movement. For example, the temporal shifting between the lower body and the upper body during a tennis serve or the change between run up to delivery during bowling in cricket.

The three models that have been discussed so far may assist to develop sufficient understanding of a skill or movement for an analysis protocol. Once the movement goal, critical features and intrinsic and extrinsic factors influencing the athlete and the performance environment have been identified, the analyst can develop the plan for when these aspects should be evaluated, as proposed by McPherson (1996).

85 Organising the information that has been collected about an event will lead to a more thorough understanding and a more logical analysis method. None of the qualitative movement analysis methods that have been reviewed here have described a process whereby the information that has been collected can be organised in a logical manner according to the focus (performer) or time of occurrence.

Figure removed due to copyright restrictions

Figure 3.8: An approach to qualitative movement analysis for performance intervention (modified from McPherson (1996))

Haddon’s matrix was first published in 1968 as a method of evaluating aetiology of injuries from descriptive terms. The article was recently republished without amendment (Haddon, 1999). The matrix represents a useful method of arranging and identifying potential factors collected during the first three steps of McPherson’s (1996) model and assigning them to the participants involved in the event and arranging them temporally with reference to the event of interest (Pre- event, event, post event). The injury aetiology models that were presented in Chapter Two are representative of other tools that may be used to organise the information.

86 Qualitative analysis is widely used in coaching for technique correction, for the adjudication of the quality of performance in sports such as diving and gymnastics, and in the human movement sciences. It has also been used in clinical applications (e.g. gait analysis and workplace monitoring). Methodological differences exist according to the targeted of study and the purpose of the qualitative analysis. The following sections will review applications of qualitative analysis in athletic and clinical purposes.

3.5.5 Qualitative Analysis of Sporting Skills

Qualitative methods of investigation have not been commonly reported in sports science research. A limited number of analysis protocols have been developed to investigate soccer (Andersen, Floerenes, Arnason, & Bahr, 2004; Andersen, et al., 2003), European handball (Oehlert et al., 2004) and Tae Kwan Do (Koh & Watkinson, 2002). At the time that this research commenced, two studies had used qualitative protocols to evaluate injury risks in the tackle (McIntosh, Savage, et al., 2005; Wilson, et al., 1999). The aim of the protocol in all five studies was to investigate the causes of injury. All studies used video for the analysis. The results of the research with respect to injury in the tackle in rugby union has been discussed elsewhere in this thesis section 3.4.1. This section will review the methodology that was used in these studies and identify variables that were used in the investigation, the organisation of the variables and the methods for testing agreement.

McIntosh et al. (2005) conducted a study to evaluate injury incidence in the tackle and other match events according to predetermined criteria. The study evaluated tackle events from video of 106 schoolboy (under 15 and under 18 years) and colts (under 20 years) rugby matches. The fields and variables that were used in the study to describe the tackle are presented in Figure 3.9. The fields are divided into nominal, categorical and reference field types. The matches were initially reviewed by one rater to identify and evaluate ‘medical events’ that occurred in the tackle. Medical events were injuries, verified by prospectively collected injury data, and knockdown events where the player was knocked over and did not immediately get

87 Field description Field type Field variables Game identifier Reference Game number or game date Event reference Reference Time of event or video counter code Player club Nominal Club name Player position Nominal Jersey number Head protection Categorical x No headgear x IRB approved headgear x Modified headgear Opposition club Nominal Club name Age group and grade Categorical Under 15, Under 18; A or B etc. Injury record number Reference Prospectively collected Injury data record number Area struck Categorical x Chin/lower face x Upper Arm (also divided into x Crown (head) x Elbow right and left side) x Face x Lower Arm x Frontal Lobe x Wrist x Temporal Lobe x Upper Leg x Occipital Lobe x Knee x Neck/Shoulder x Lower Leg x Abdomen x Ankle x Back x Unknown x Torso x See comment x Pelvis

Striking object Categorical x Opponent body region (same as area struck, above) x Ground x Fixed object x Spectator x See comment x Unknown Direction of injured Categorical x Moving forward player x Backwards x Sideways x Swivelling x Stationary x Unknown Head movement Categorical x Extension x Flexion x Lateral flexion x Rotation x Unknown Collision description and Comment additional comment Suitable for Dichotomous Yes/no biomechanical analysis Figure 3.9: Fields included in video analysis of the tackle by McIntosh, et al. (2005)

88 up to continue play. Examples of good and poor skill execution were also evaluated. Measures of reliability were not described.

The authors reported on 233 tackles that were coded from the matches in the study. Of these tackles, 130 were coded where a medical event did not occur. These 130 tackles were described by fewer fields as examples of good and poor tackling technique. One hundred and three (103) medical events (injuries and knockdowns) were identified from the video. All medical events were completely coded using the fields presented in Figure 3.9. The analysis described the player (club, age group, and position), the impact (area struck, striking object and direction of injured player) and details describing concussion injury (headgear, head neck movement). Of the 103 medical events, only 32 injury events were successfully linked with injury data (31%). In addition to the fields presented in Figure 3.9, the authors recommended collecting information on the condition of the ground, field position, if it was a multiple impact (simultaneous or sequential) tackle, if the tackle was illegal, and providing for multiple body regions to be struck and additional striking objects.

The aim of the study by Wilson and colleagues (1999) was to describe the circumstances of tackle injury by providing additional information about the movement of the injured and non-injured player in the tackle and a comparison to prospectively collected injury data. The schema of their analysis method is presented in Figure 3.10. The analysis consisted of five fields evaluating:

x the role of the player (Ball-carrier or Tackler) x player action at the time of the tackle (running, jumping, diving etc) x the type of tackle (smother, stopping, trip or shoulder charge) x selected key features of the tackle and technique x injury risk factors (collision with ground/other or intrapersonal twisting)

The protocol was developed from epidemiological data (Bird, et al., 1998) and broadly describes skill execution and injury risk in the tackle using specific terms.

89 Figure removed due to copyright restrictions

Figure 3.10: An analysis of tackling (Wilson, et al., 1999)

90 The authors identified four types of tackles and the selected key features included a description of falling and the injury factors were evaluated through four field variables assessing how the load deemed to be related to the injury was applied to the player. Video of 28 injury incidents were evaluated during the study by two analysts that had knowledge of the game. The incidents were viewed jointly by both analysts until they were able to reach agreement on the fields in the analysis.

The football incident analysis (FIA) was developed by Andersen et al. (2003) to investigate the circumstances that create high risk situations and mechanisms of injury in soccer. FIA uses 19 categories which can be combined in five groupings of similar categories:

x The injured player x Match situation x Attacking play x Defensive play x Field position

The fields used in the analysis are presented in Figure 3.11. The injured player was described in terms of their playing position, their role, movement direction and action with the ball. The match situation was described with the time of the match, the type of match, the team in possession and actions of both teams in the lead up to the event. Other fields were dedicated to describing the type of play of both teams in soccer specific terms and field position. The authors did not elaborate on the process for developing the analysis fields.

To test inter-rater reliability of FIA, two experienced soccer coaches were asked to code 52 injury risk incidents. The two raters completed the coding independently and agreement was measured using a Kappa coefficient (ț). The inter-rater agreement for all fields was good (ț=0.61 to 0.8, n = 10) to very good (ț > 0.81, n = 9). The authors did not report on possible reasons for the agreement findings or the process that was used to select aspects of the skill that were investigated and develop the fields for their assessment.

91 Categories Variables Ball possession x Attack x Defence Attack type x Set plays x Breakdowns x Long attacks x Long attacks, including long pass Positioning x One on one situation i.e. number of players x Not one on one situation involved Team passing action before x Long pass injury risk incident x Short pass x Cross x Deflection Field position x Defensive third i.e. zones on the playing field x Midfield zone x Attacking third x Score box Attack effectiveness x Effective attack x Ineffective attack Ball winning situations x Attempting to regain possession x Immediately after regaining possession (up to 5 s) x Regaining possession after deflection from opponent x Not ball winning situations Degree of balance in x Good balance opponents’ defence x Average balance x Poor balance Player role x 1st defender x Other defender x 1st attacker x Other attacker Playing position x Goalkeeper (i.e. static positions of players x Fullback on the field based on playing x Central defender formations) x Wing midfielder x Inside midfielder x Central midfielder x Striker Type of individual action with x Dribbling the ball x Heading x Receiving the ball x Screening tackling x Turning, x Flicking (using foot or head), x Passing x Goalkeeper action, x Shooting

92 Categories Variables x Blocking x Clearing x Ball to body accident x Unclear action x No action with the ball Degree of ball control after x High level of control receiving it x Low level of control Player’s movement direction x Forward x Sideways x Backward x No movement Player’s movement intensity x High intensity (sprinting and high intensity running) x Low intensity (jogging and walking) Duel type x Heading duel (active or passive) x Tackling duel (active or passive) x Screening duel (active or passive) x Running duel x Other (e.g. Pushing, kicking, stepping, collision) x Not in duel Attention x Attention towards primary duellist x Attention towards the ball - On the ground (ball in contact with the playing surface) - In the air (ball at head height and upwards) - ball between head height and playing surface x Attention towards team mate - Near (in the vicinity of the ball) - Further away (not in the vicinity of the ball) Tackling type x Being tackled x Not being tackled x Tackling x Not tackling Type of incident risk action x Against 1st attacker towards “back room” x Against 1st attacker elsewhere x Against 1st defender x Action away from the ball x Actions against other players (2nd and 3rd attackers and defenders) Referee’s decision x Free kick for x Free kick against x Yellow card x Red card x No foul called

Figure 3.11: Fields included in Football incident analysis (FIA), Andersen et al. (2003)

93 The FIA was used in two subsequent studies of injury in soccer (Andersen, Engebretsen, & Bahr, 2004; Andersen, Tenga, et al., 2004). Andersen and colleagues also investigated ankle injuries in soccer using an analysis protocol that included some fields common to the FIA, but was developed specifically for the purpose (Andersen, Floerenes, et al., 2004). The fields that were used in the analysis method assessed:

x the primary injury mechanism (soccer specific skills) x player movement intensity at the time of injury (high or low) x role of the player injured (Tackler or being tackled) x tackle type observed (soccer specific tackles) x if the tackle was late x time of contact with opponent with reference to injury (before, after etc.) x primary direction of ankle motion (inversion or eversion etc.) x point of impact at the ankle on the injured player x position of the foot (on ground or in the air) x degree of weight bearing (full, moderate or minimal) x referee’s decision (legal, severity of infringement)

Injury data were collected prospectively by assisting medical staff and ankle injuries were selected to be identified from video of the matches. Forty six ankle injuries were recorded during the study and 26 (57%) were successfully linked with video. Two raters coded the 26 injury events independently before reviewing the results together to resolve disagreements between their observations. The authors noted that video analysis provided valuable information about ankle injury mechanisms.

Oehlert, et al. (2004) evaluated video 59 injury events occurring during elite male European handball. An injury event was deemed to have occurred where:

x the game was stopped by the referee because of injury to a player x the player fell to ground x the player received medical aid

94 The analysis protocol was developed to assess ACL injury aetiology from video. In this study, the protocol was used to describe knee injuries as well as injuries to other body regions. The analysis protocol consisted of nine fields, three of which were used to specifically describe ACL injury risk (Figure 3.12). The fields that have been used in the analysis protocol can be grouped according to those describing the player role, the match situation, impact and injured region. The authors did not elaborate upon the development of the analysis protocol.

Fields Variables Player x Goal keeper x Field player Body region x Head/neck x Thorax/abdomen x Pelvis/hips x Upper arm x Lower arm x Hand x Upper leg x Knee x Lower leg x Foot If the knee was the region struck Knee stretch x 0–30° x 30–60° x >60° Site of the impact to the knee x Behind x Above x In front Knee valgus Yes/No Position on court x Right x Half-right x Middle x Half left x Left x Back area x Inside circle Playing situation Attack Defence Contact with another player? Yes/No Loss of balance Yes/No Other comments (text)

Figure 3.12: Fields included in video analysis of handball injuries by Oehlert, et al. (2004)

95 Two raters were responsible for reviewing and coding the injury events with the analysis protocol. In place of objective measures of agreement, the study used a review method to ensure validity of the results, similar to that used by Wilson et al. (1999). Raters reviewed all events together at normal speed and in slow motion before preparing their analysis of the events separately. Upon completing their analysis of the injury events, the raters discussed differences in their analysis until they reached agreement. Information about the reliability of individual fields was not presented in this study; however the authors did note that it was difficult to objectively assess the severity of an injury event accurately.

Finally, Koh and Watkinson (2002) presented a protocol that was developed to describe the circumstances of impacts to the head in Taekwondo. The authors presented a number of inclusion and exclusion criteria for analysed events, demonstrating the refined focus of their analysis from a whole skill evaluation to a specific event. The criteria presented include variables describing the movement or non-movement of the head and neck following a blow to the head, the referee’s decision regarding the legality of the blow and an assessment of whether a concussion occurred. The analysis protocol uses 15 fields to analyse the blows to the head and face which met the selection criteria from 48 matches. The fields used in the analysis are presented in Figure 3.13. The fields can be broadly grouped according to those fields assessing the impact, fields assessing severity measures, fields describing the athlete, and fields concerning the match situation. The authors did not elaborate on the development of analysis fields or field variables.

Reliability of the protocol was measured in the study using percentage agreement amongst three raters. The three raters analysed five events to test reliability of eight of the analysis fields. Inter observer reliability in these fields was reported as 97%. The authors identify the assessment of relative size of two opponents as the only field where there was disagreement. All other fields including symptoms of concussion, kicking technique and kicking type had 100% agreement. The fields with highest agreement did not necessarily use dichotomous responses, although generally the fields contained between two and three categorical responses.

96 Category Indicator Height difference* x Taller x shorter x about same Kicking technique* x Axe x Roundhouse x turning-round house x spinning x back x side kick Head blow situation a. Attacker's fighting type* Offensive / defensive b. Attacker's kicking type x Single x double x combination kick type c. Attacker's dominant side of leg Left / right d. Receiver's fighting type* Offensive / defensive e. Receiver's kicking type x Single x double x combination kick type f. Blocking skill* Used / not used g. Sparring stance (position) Closed / open stance h. Which side of the foot in front Attacker: left / right foot Receiver: left / right foot Head displacement* Yes / no Displacement direction: ____ Anatomical site of impact* x Side or back of the head/face/jaw Problems post impact* x Balance (including fall, off-stance, etc.) x Gait problem x No change Number of blows to the head* 1 / 2 / 3 / 4 / 5 / 6 / 7 head blow(s)

Figure 3.13: Video analysis fields used to evaluate blows to the head and face in Taekwondo (Koh & Watkinson, 2002) * Fields assessed in reliability testing

The number of studies that were identified in the search presented in section 3.1 was limited. One reason for the lack of breadth of studies may be concerns about the validity and reliability of qualitative or subjective methods of analysis that were discussed in section 3.5.3. The time consuming nature and associated costs of performing qualitative analysis and the lack of an alternative explanation may be that alternative methods are being utilised to evaluate more complex movements

97 and describe injury situations (Krosshaug, et al., 2005). However, it is common in professional sport to use video analysis to evaluate player and team performance and this resource is widely used in professional rugby. Somewhat surprisingly, the tackle in rugby union is represented twice in the five studies of sporting skills that have been reviewed. Unfortunately, none of the studies that were reviewed presented a description of the process that was used to develop the qualitative analysis method. However, in all of the studies the analysis fields could be grouped into those evaluating aspects which were common. These analysis groupings were:

x The player (size, position, age group, etc.) x The impact (nature of the collision, body region struck, speed of movement, direction of the opponent, etc.) x The match situation (position on the field, attacking or defending, time in the match etc.) x Specific information about the event (i.e. the type of tackle, etc.) x Outcomes (loss of balance, apparent injury or symptoms, etc.)

A number of studies have assessed skill execution and technique in sporting skills, however these have generally presented performance variables and have not assessed the reliability of the method (e.g. Knudson & Morrison, 1996). Only a small number of studies have assessed injury risk in sport. The majority of studies have attempted to assess reliability and or validity of their protocol, however, at the time that this research commenced there was no uniformity in the measures that had been used. Only two studies that have been discussed in this section have used a formal statistical process to assess inter rater reliability, or agreement. At least two other investigations occurred in soccer which utilised percentage agreement, but these provided scant information about the analysis protocol that was used and have not been discussed (Fuller, Junge, & Dvorak, 2004; Fuller, Smith, Junge, & Dvorak, 2004). Of the other research that was discussed here, one study used percentage agreement and one study used Kappa. Three studies used consensus agreement between raters to resolve differences and provide an informal reliability process and validation of the results. One study did not measure agreement.

98 3.5.6 Qualitative Analysis of Non-Sporting Movement Tasks

The literature search that was presented in Chapter Three was expanded to identify examples of qualitative technique analysis in other disciplines to supplement the limited number of examples of applications in sport that had been identified. Keyword searches for “qualitative motion analysis” and “qualitative movement analysis” returned over 1000 articles. Eighty nine articles in languages other than English were excluded (in Endnote TM). Scrutiny of abstracts from a random selection of 100 of the remaining articles indicated that the majority of the research presented in these citations were from fields such as chemistry, biology and behavioural sciences and generally irrelevant to movement analysis. To refine and focus the search, additional search terms were applied to the citations using Endnote. Limiting the search to “biomechanic” and “reliability” returned 112 and 23 articles respectively. Limiting the results with the term “industrial” returned 7 articles, and the majority of these described irrelevant applications of qualitative analysis. The results of the search were discarded and the peer reviewed journals ‘Ergonomics’ and ‘Applied Ergonomics’ were targeted and the table of contents manually scrutinised to identify relevant search terms. The reference lists of relevant papers were further scrutinised to identify relevant literature. This process identified a total of 11 articles evaluating qualitative technique analysis for clinical and ergonomic applications.

The non-sporting studies that were reviewed were chosen because they used formal methods of assessing reliability. A summary of the research that was included in this section is presented in Table 3.6. The results are presented alongside the sporting studies that were identified in section 3.5.5 for comparison. Qualitative analyses have been used in ergonomic applications, such as the Rapid Upper Limb Assessment tool (RULA) and, more recently, the Quick Exposure Check (QEC) to evaluate postures that were used during manual occupational tasks investigate exposure to risk factors for postural injury (David, Woods, Li, & Buckle, 2008; McAtamney & Nigel Corlett, 1993). A number of studies have also been conducted in clinical settings, particularly in the field of observational gait analysis. Several of

99 the studies provided limited insight into the methods that were used to develop their analysis protocols and many of the studies consulted a panel of experts during the development to validate the analysis protocol. There is support for the inclusion of epidemiological review when developing a qualitative analysis protocol and identifying and prioritising injury risk factors and other relevant information (C. D. Burt, Henningsen, & Consedine, 1999; David, et al., 2008; Ketola, Toivonen, & Viikari-Juntura, 2001). Developing the tool from existing methods and through observation of the postures adopted, and biomechanical assessment of muscle actions and forces required during the targeted action also has support (C. D. Burt, et al., 1999; Ketola, et al., 2001; McAtamney & Nigel Corlett, 1993).

The statistical methods that were used to assess reliability of the protocols varied from study to study and were generally dependent upon the number of raters and types of field variables that were used. The number of fields ranged from 1 to 30 and, while 7 of the 18 studies in Table 3.6 assessed agreement between two raters, the number of raters ranged between 2 and 120. In discussing the results of reliability testing, an interesting trend was reported for estimating joint position (Baluyut, Genaidy, Davis, Shell, & Simmons, 1995; McAtamney & Nigel Corlett, 1993). There was high consistency in agreement except where movements were between, or on the border of, defined ranges, particularly when the elbow was at 90°. The authors concluded that it is more difficult to evaluate particular body regions (the upper extremity) compared to others (the lower back and neck). Additionally, flexion and extension were easier to evaluate than other postures while the position of the lower extremity affected the accuracy of postural estimation of upper body and upper limb (Baluyut, et al., 1995). Agreement of parameters of dynamic movement or subtle changes in movement or can also be poor (Knudson, 1999). For example, Andersen et al (2003) found high agreement (ț = 0.81) evaluating running velocity based on extremes (e.g. running vs. walking) rather than including a separate field to assess intermediate values (e.g. medium pace or jogging). Methods of assessing reliability and validity will be discussed in the following section.

100 Author Activity Subjects Raters Fields Scale Agreement Andersen, et al. Soccer 52 2 19 categorical Kappa (2003) Andersen, Floe- Soccer 26 2 11 categorical Consensus renes, et al. (2004) agreement Baluyut, et al. Posture 1 63 30 categorical PA (1995) Brunnekreef et al. Gait 30 10 12 dichotomous ICC (2005) Brunton, et al. MCP 2 40 1 scalar ICC (1999) angle Burt & Posture 70 2 18 dichotomous PA, ICC, Punnett.(1999) Kappa, GLM David, et al. (2008) Posture 18 18 8 Kappa, PA

Fuller, Junge, et al. Soccer 232 4 7 categorical PA (2004) Fuller, Smith, et al. Soccer 857 2 3 categorical PA (2004) Holmefur, et al. Clinical 18 2 22 ordinal ICC (2007) Keenan (1996) Clinical 14 5 1 to 4 categorical Kappa (5 pairs) Ketola et al. (2001) Posture 14 2 6 dichotomous Kappa, PA

Kibler (2002) Posture 26 4 1 categorical Kappa (2 pairs) Koh & Watkinson Tae- 5 3 8 (15) categorical PA (2002) kwondo Krosshaug, Nak- Knee 3 6 10 continuous/ SD amae, et al. (2007) (27 trials) scalar McAtamney (1993) Posture Not 120 11 ordinal Not reported reported Oehlert, et al. Hand- 59 2 9 categorical Consensus (2004) ball agreement Read, et al. (2003) Gait 5 5 17 interval & PA, Kappa (10 pairs) ordinal Wilson et al. (1999) Rugby 28 2 5 categorical Consensus union agreement

Table 3.6: Summary of research using qualitative technique analysis and incorporating reliability testing (ICC = Intraclass correlation coefficient, GLM = Generalised linear modelling, PA = Percentage agreement)

101 3.6 Validity and Reliability in Qualitative Analysis

Validity is defined by Patton (2002; page 14) as:

“An accurate reflection of the analysis to what has occurred or that the protocol measures what it is supposed to measure.”

Knudson and Morrison (2002) refer to logical validity in qualitative analysis through developing a description of the skill through consultation with experts and the literature. This is similar to the systematic development process that was reviewed in section 3.5.3 and can be summarised as deconstruction of the movement by identifying critical features of technique and developing a method to accurately describe each component. Knudson and Morrison (2002) also identify criterion referenced validity for qualitative analysis, where the protocol is compared with a known standard.

Reliability, or agreement, is the consistency in results obtained when the analysis is applied by different observers (inter-rater reliability) or by the same rater across over a period of time (intra-rater reliability) (Kirkwood & Sterne, 2003). The predisposition of data obtained through human judgement to measurement error caused by an individual’s perception has been discussed as the primary weakness of qualitative analysis (Shrout & Fleiss, 1979). Reliability of qualitative analysis may improve by increasing the number of analysts and trials used and providing extensive training and practice with the protocol being used. It may also improve with clear identification of what is to be analysed and definition of the measures or method of assessment (Knudson & Morrison, 2002). Several authors have indicated that the reliability of an analysis field improves where dichotomous variables (e.g. yes/no) are used in preference to open ended or continuous responses, which reduce agreement (Ketola, et al., 2001). Additional confidence in the reliability of a protocol can be developed through triangulation, i.e. assessing the same parameter in different ways (Patton, 1999). To demonstrate that the raters are able to apply the protocol as intended and that results may be interpreted with

102 confidence, the agreement of the protocol should be examined with an appropriate reliability measure.

3.7 Methods of Assessing Reliability for Qualitative Scales

The qualitative technique analysis research reviewed in sections 3.5.5 and 3.5.6 used a number of different methods of assessing the agreement between raters (Table 3.6). The methods used to assess agreement incorporated both numerical measures and non numerical methods. Ergonomic and clinical research used numerical measures of assessing agreement more frequently than sports science research, where a consensus process between two raters was common. The choice of method available to assess agreement depends on the methodology used in the study and is influenced by the number of raters judging the event, whether the same or different raters were used to judge each event, the number of events and the nature of the field variables used to assess traits (categorical/nominal vs. continuous/scalar). The methods that will be reviewed in this section are:

x Consensus agreement x Standard deviation x Percentage agreement x Variations of chance corrected percentage of agreement (Kappa) x Intraclass correlation coefficients

Consensus agreement, where raters discuss points of difference in their observations to reach a unanimous verdict, has been used in sport, ergonomic and clinical evaluations. It has commonly been used in investigations with a small number of fields (between 5 and 11), when training raters in the application of the protocol, or to assess criterion referenced validity of the protocol (Brunnekreef, et al., 2005; S. Burt & Punnett, 1999; Oehlert, et al., 2004; Wilson, et al., 1999). For obvious practical reasons, this method cannot be used when a research tool consists of a large number of analysis fields, where a large number of raters are

103 involved during frequent assessments or where it is released widely for use outside of a particular research group.

Four studies have assessed intra-rater reliability by evaluating the standard deviation (SD) of the difference between two values for the same target evaluated a number of weeks apart. All of the studies assessed agreement between measurements on a continuous scale. Krosshaug, Nakamae et al. (2007) used standard deviation as a measure of agreement in their study where several raters were asked to assess the magnitude of kinematic variables. The other three studies were time motion analyses of rugby union where the aim was to monitor distance travelled and duration of activity rather than categorical variables (Deutsch, et al., 1998; Duthie, Pyne, & Hooper, 2003b; McLean, 1992).

Percentage agreement, or proportion of agreement, is the proportion of cases in which raters agree for a given trait and target. Calculating percentage agreement is relatively straightforward and it provides a flexible method that can be used to evaluate agreement between any number of raters. Percentage agreement can also be applied to a number of data types, including nominal or categorical data. The equation for calculating the mean percentage agreement ( P ) for N targets amongst multiple raters was presented in Fleiss (1971) as:

N k 1 2 P ( ¦¦ ij  Nnn ) nNn  )1( i j 11

Where n is the number of raters, j is the number of categories or fields rated (where j = 1,…,k), and i is the number of subjects (i=1,…,N). Depending on the methodology whether a constant of varying panel of judges is used, the results can be generalised to indicate agreement expected for any user of the tool (Fleiss, 1971). Where a constant panel of the same judges is used, agreement cannot be generalised beyond those judges.

Percentage of agreement has been described as an inadequate method for measuring agreement because it does not take into account agreement occurring by chance, and therefore may overestimate agreement as a result (S. Burt & Punnett, 1999).

104 Chance agreement may occur in situations where the rater makes a complete guess during a particular evaluation or where the rater is unsure and makes an assessment based partly on a guess or what they expect to happen based on personal experience (Uebersax, 2009). Despite this limitation, percentage of agreement gives an initial indication that may be used for comparison, either with other studies and protocols, or to evaluate the evolution in reliability and it remains one of the most widely used measures of reliability (Table 3.6). Further, it has been noted that overestimation of agreement is reduced in fields using more than two field variables (Uebersax, 1987). Conceivably, the use of multiple judges should also reduce the probability of chance agreement.

Percentage agreement can be corrected to address chance agreement and the methods used to calculate are known as Kappa (N ). There are a number of variations of Kappa depending on the number of raters and methods used (to determine which judges) of codings. Each variation follows the formula:

 PP N co 1 Pc

Where Po is the observed percentage of agreement and Pc is the agreement expected due to chance. The variation of Kappa arise in the method used to calculate Pc. Assessment of agreement between two raters for an item using a categorical or nominal scale is normally performed using the statistics Kappa or weighted Kappa (Cohen, 1960, 1968). Both of these methods incorporate a correction for agreement which may occur through chance alone. However, Cohen’s Kappa may only be used to assess agreement between two raters or for pairs of raters and has been used to assess agreement in between one and nineteen fields (Table 3.6). A scale for interpreting Kappa values is presented in Table 3.7.

Fleiss (1971) presented a generalisation of unweighted kappa which examines the agreement amongst multiple raters assessing a target on a nominal or categorical scale. This generalisation is intended to be used where a constant number of judges are used, but the judges for each subject or target are different. The method is

105 therefore not applicable for cases where a constant panel consisting of the same judges has been used to rate a target.

Intraclass correlations (ICC’s) have been presented as a method of evaluating agreement of items assessed with continuous measurement scales (Shrout & Fleiss, 1979). ICC’s have been used in four of the clinical studies that were reviewed, but no sporting study had used this method at the time that this research commenced. There is no limitation of the method that would prevent its application to sporting skills and it was recently applied to assess agreement in injury identification (Twomey, Finch, Doyle, Elliott, & Lloyd, 2010). Six models of ICC are outlined by Shrout and Fleiss (1979):

1. Each item is evaluated by different raters who are randomly selected from a larger pool of judges

2. Each item is evaluated by the same raters who are randomly selected from a larger pool of judges

3. Each item is evaluated by the same raters who are the only raters used

ICC is calculated from an analysis of variance model to assess the reliability of either judges (intra rater-reliability or consistency) or fields (inter-rater reliability or agreement) (McGraw & Wong, 1996; Shrout & Fleiss, 1979). Because this method uses an ANOVA to develop the ICC the variables analysed need to be continuous so that representative means can be created. As a result, ICC’s cannot be utilised when assessing agreement in nominal or categorical data. ICC can be used to assess agreement for dichotomous data.

The coefficients of agreement have been interpreted by many studies according to a arbitrary scale presented by Landis and Koch (1977). The scale was developed for interpreting Kappa values (Table 3.7), however, it has also been used to interpret the results of other measures of agreement and has recently been used to interpret ICC values (Twomey, et al., 2010). It may be possible to use an adjusted scale to assess agreement for other measures including percentage of agreement.

106 Kappa Statistic Strength of Agreement < 0.00 Poor 0.00-0.20 Slight 0.21-0.40 Fair 0.41-0.60 Moderate 0.61-0.80 Substantial 0.81-1.00 Almost Perfect Table 3.7: A scale for interpreting values of the Kappa statistic

3.8 Chapter Summary

The review of epidemiology research in rugby union identified common injury trends and confirmed that the tackle was the event most often associated with injury (Bird, et al., 1998; Brooks, et al., 2005a; Durie & Munroe, 2000). Focussing on the results of these epidemiological studies for the tackle revealed that the event conformed to the most common trends, however some specific injury risk factors were observed and others were postulated. Poor skill execution, training and player experience have been attributed as causes of injury in many sports and also in rugby union. Ground and environmental conditions have been suggested to influence injury aetiology as may a number of match variables. At the time that this research commenced, there had been few investigations of the tackle and tackling in rugby union.

In addition to the description of tackle injury from the prospective of whole sport injury surveillance, the number of tackles per match had been enumerated, contact forces applied to the Tackler estimated, and there had been two attempts to describe injury situations in the tackle using qualitative methods. The performance of specific skills in the tackle and player interaction at the tackle event had not been subjected to rigorous evaluation and the circumstances and actions that constituted a representative tackle had not been evaluated. While the representative tackling style has not been evaluated, coaching material presents the shoulder tackle as the safest and most effective method of tackling an opponent. Additional tackling methods and terminology have been identified and used in other media, the terms smother, or front-on tackle, and ankle tap are commonly used to describe tackling styles

107 during television broadcasts and during personal communication with coaches. But coaching manuals do not identify or describe these other tackling methods. How often techniques other than the shoulder tackle are utilised in a game situation has not been quantified. Further, it is likely that the tackling technique that players practice during training changes with the altered tempo-spatial constraints of a match, or to maintain a competitive advantage in the tackle and the ensuing ball contest. This information is important for understanding the skill and injury situations and for injury prevention and several authors have supported a requirement for a comprehensive description of tackle techniques.

The difficulties in evaluating the tackle and the aetiology of tackle injuries have been discussed earlier in this thesis (section 3.4.5). As with many other complex sporting skills, quantitative investigations of the tackle are constrained by the multi- factorial nature of the skill. As a collision event, many aspects of the tackle can be obscured by the players involved and present optical marker based tracking systems have a limited application because of probable marker detachment during contact between players. Quantitative methods are not practical for preliminary studies that aim to develop a global understanding of an event and are better suited to examining discrete variables. Qualitative analysis is better suited to investigations where the objective is to develop broader understanding of events and to refine the subject of investigation to allow for the use of quantitative methods (Patton, 1999). A qualitative analysis protocol was selected as the most appropriate method to analyse the tackle. The qualitative methods used by Wilson and colleagues (1999) and in a pilot study of the tackle by the research group of which the Master’s candidate was part (McIntosh, Savage, et al., 2005) were adjudged to describe the event in insufficient detail. Developing the analysis protocol through an objective and systematic process and testing reliability may address problems of poor reliability and user bias. None of the studies that have been reviewed in the literature review subjected an analysis protocol to two rounds of reliability testing. The remainder of this thesis will describe the process of developing the analysis protocol and the results of two rounds of formal reliability testing and the application of the protocol to a sample of tackles.

108 CHAPTER FOUR

DEVELOPMENT OF A PROTOCOL FOR THE

QUALITATIVE ANALYSIS OF THE TACKLE

When developing a qualitative analysis protocol, rigorous preparation of the method is essential in producing a useful analysis tool and preventing bias (Arend & Higgins, 1976; Knudson & Morrison, 2002). Proper preparation should incorporate the collection of information to develop a description and understanding of the tackle and organisation of the information according to biomechanical and epidemiological principles (i.e. the player affected, intrinsic and extrinsic variables and temporally). The primary objective of the research that is presented in this chapter was to develop a valid analysis method through a repeatable, systematic process that drew upon the frameworks and incorporated the information that had been identified during the review of literature. This chapter will describe the process undertaken to develop the qualitative analysis protocol for the tackle and present the result of that process.

4.1 Methods

The tackle analysis protocol was developed in line with the recommendations of Patton (2002) using the existing qualitative analysis guidelines and frameworks of Arend and Higgins (1976), Hay (1988), Knudson and Morrison (2002), McPherson (1996), Patton (1999) and Sofaer (1999). The development process that was followed for this research, which corresponds with the first step: Preparation; of Knudson and Morrison’s systematic model (Figure 3.5), can be summarised in six steps:

109 1. Developing a definition to identify events for analysis (section 4.2.1) 2. Evaluation of existing methods of qualitative motion analysis for the targeted skill (section 4.2.2) 3. Developing an understanding of the movement or skill by identifying the movement goal, critical features of technique and potential risk factors for injury (section 4.2.3) 4. Systematic organisation of the information (temporal phases and player or performance environment focus; section 4.2.4) 5. Quantification and/or categorisation of the identified skill parameters (i.e. how the fields will be assessed; section 4.2.5) 6. Informal validation through presentation of the method to an expert panel (section 4.3)

Further decomposition of the development process may occur at each of the six steps to assist in the development of an analysis protocol; for example, additional steps that are specific to the targeted skill may be required when developing an understanding of the movement or skill or organising the information. The development process will be outlined in this section and the results of each procedure are presented in sections 4.2.1 to 4.2.4.

To achieve consistency in the events analysed with the analysis protocol, the nature and type of desired events, i.e. the desired targets for analysis with the protocol, were considered and a definition of the tackle event was prepared accordingly. The purpose of defining the event is similar to that of injury definitions for epidemiological projects, which was described in the previously published consensus statement as establishing consistency and allowing comparison of data between epidemiological studies (Fuller, Molloy, et al., 2007). To develop the tackle definition for the study, the rules of rugby union and English dictionaries were consulted. Existing methods of qualitative motion analyses for sporting skills that had been identified in the literature search were reviewed.4 From the review of these studies, the type and nature of the variables that were used to assess aspects

4 Methods for identifying the research and the results of the review are presented in section 3.1 and section 3.5.6.

110 of player skill and the environmental constraints of the task, as well as the organisation of the analysis fields were used to inform the development of the fields, field variables (see list of terminology, page xx) and structure of the tackle analysis protocol.

Once the tackle definition had been established and the preliminary investigation of existing qualitative motion analysis methods was complete, the focus of the development process transferred to constructing the fields and field variables that would provide a detailed description of the tackle. Determining the nature of the fields and field variables required a detailed understanding of the tackle event and was conducted according to the pre-observation phase of the frameworks presented by Arend and Higgins (1976) and McPherson (1996). The tackle was deconstructed to develop knowledge of the activity through identifying the goals of the tackle for the Ball-carrier and Tackler, the constraints of the performance environment and the biomechanical factors contributing to successful skill performance and/or injury aetiology. This served to inform both the fields that are used in the analysis and the field variables that were used to quantify and describe the skill or event being analysed. The process used to deconstruct the skill and develop understanding of the tackle can be summarised in five steps:

1. Identification of the movement goal 2. Identification of critical features of technique for skilled performance 3. Match factors and weather and environmental considerations 4. Review of injury patterns from epidemiological literature to inform aetiology 5. Consideration of critical features of technique and injury patterns from a biomechanical perspective

Figure 4.1 is a graphical representation of the interaction between the groupings and their contribution to the development of the analysis protocol. Critical features of technique were defined previously in this thesis (section 3.5.4). The critical features of technique and match and environmental factors that affect the performance of the tackle were identified through a review of coaching material

111 prepared by the Australian and New Zealand Rugby Unions (ARU, 2006a, 2006b; NZRU & ACC, 2005a, 2005b). A coaching seminar, developed by the ARU to instruct coaches in practice methods for the safe development of skills, was also attended by the Master’s candidate. From the coaching material and sessions, a list of the recommended critical features for skilled performance was compiled for both the Ball-carrier and Tackler. This information was then arranged temporally, in phases (preparation, action, and follow-through) according to a common coaching method. The influence of match and environmental factors were considered from the perspective of performance of the tackle skill.

Biomechanical factors

Critical features of Injury technique aetiology Tackle event

Match and Player Environmental (Intrinsic) (extrinsic) factors factors

Figure 4.1: An outline of the process used to develop the tackle analysis protocol. All factors that were investigated for their contribution to the tackle were considered from the perspective of both the Ball-carrier and Tackler/s. Additionally, critical features of technique and patterns of injury were considered from a biomechanical perspective.

112 Once critical features had been identified, they were considered from both epidemiological and biomechanical perspectives to develop insight into how they should be evaluated and identify additional analysis targets. The epidemiological perspective was evaluated by identifying injury patterns from data obtained through the Rugby Union Injury Surveillance Study (RUISS), a longitudinal, prospective injury surveillance study (McIntosh & Savage, 2005). To ensure that the protocol could accurately describe common injury situations, the expected circumstances of aetiology for these injuries were determined; e.g. direct impact for concussion, fall to an outstretched limb for shoulder dislocation or upper limb fracture. Potential contributing factors for injury in less obvious circumstances were identified and assigned as either extrinsic or affecting a player (intrinsic) (Bahr & Krosshaug, 2005; Meeuwisse, 1994). The information that had been collected was then arranged using Haddon’s matrix (Haddon, 1999). The biomechanical parameters of the tackle were assessed by developing free-body diagrams of tackles to investigate the forces acting on the Tackler and Ball-carrier during the tackle. The biomechanical basis of the advocated skills and movements were also evaluated using a hierarchical analysis (Hay & Reid, 1988).

The information was then logically organised according to the categories used in other research. The analysis was divided into two parts, an upper level analysis consisting of fields evaluating global event descriptors and a lower level analysis describing skill performance and injury risk and outcomes for the players involved. The upper level would be completed for all tackle events while the lower level would be completed only when an unobstructed view of the event was available. To effectively describe multiple player tackles, where Tacklers may engage with a Ball-carrier from different directions or using different tackling techniques, each Ball-carrier-Tackler interaction was treated as a separate analysis, except where two Tacklers made contact with the Ball-carrier simultaneously.

Once a draft version of the analysis protocol had been prepared, it was presented to an expert panel of three coaches that were involved in the ARU’s high performance programs and the ARU medical director for validation and feedback. The coaches

113 who participated in the panel had a minimum level 2 coaching certification from the ARU. The panel’s comments on the protocol were incorporated in the revision of the draft protocol. The revised draft protocol was then presented to the chief investigator of a collaborating research group during a meeting in Sydney, Australia, in June 2006. The collaborating research group had independently developed a method to analyse the tackle. During the meeting the protocols were reviewed by the other group to identify contrasting priorities of the two groups and a formal definitions document and coder manual was created for reliability testing.

4.2 Results

4.2.1 Tackle Definition

Two definitions from the laws of rugby union and the Oxford English Dictionary for the tackle were presented as part of the overview of the tackle in the introduction to this thesis (section 1.1). Events selected for analysis would be different according to the definition used. The two definitions will be reviewed here as background for the selection of the analysis definition.

The tackle is addressed in law 15 which states that a tackle has occurred when:

“the ball-carrier is held by one or more opponents and is brought to ground” (International Rugby Board, 2005b).

The two important provisions of Law 15 are:

1. that the Ball-carrier makes contact with the ground; and

2. for the Ball-carrier to be ‘held’

‘Ground contact’ is defined in Law 15.3 as situations where the Ball-carrier is on their knees or sitting on either the ground or another player who is on the ground. ‘Held’ is not defined in the laws of rugby union. However, a player is considered held when they are grasped by an opponent and prevented from advancing towards

114 the try line. A limitation of using Law 15 for an analysis of the tackle is that it would lead to the exclusion of a number of events that would commonly be described as tackles or attempted tackles by coaches, match medical personnel and other observers. For example, under Law 15, a ball-carrier who breaks through contact with an opponent is not a tackled player and a tackle has not taken place. Similarly, if the Ball-carrier does not go to ground then a tackle has not taken place.

The definition that is provided in the Oxford English Dictionary (OED) was used for the analysis because it was considered to be broader, encompassing many situations that would commonly be described as tackles. The OED defines a tackle:

“To seize and stop (an opponent) when in possession of the ball.”

The definition of a tackle that was used for the tackle protocol was:

“any attempt to stop or hinder the Ball-carrier”

4.2.2 Previous Research

The basis of the tackle analysis protocol was pilot research that had been conducted by the research group of which the Masters candidate was a member (McIntosh, Savage, et al., 2005). The literature search identified two research protocols developed to investigate skill execution and injury risks associated with tackling in rugby union and seven similar studies in other sports. These works were presented and discussed in section 3.5.5 of this thesis. The fields and field variables that were used in these studies were compared and strengths and weaknesses identified and tested through application to tackling and injury situations.

Unfortunately, none of the investigations of qualitative technique analysis of sporting skills reviewed provided a full description of the process used by the researchers to develop the fields and field variables that were used in the qualitative analysis method. However, in all of the studies the analysis fields could be grouped into those evaluating aspects which were common:

115 x The player (size, position, age group, etc.) x The impact (nature of the collision, body region struck, speed of movement, direction of the opponent, etc.) x The match situation (position on the field, attacking or defending, time in the match etc.) x specific information about the targeted event (i.e. the type of tackle, kick or other movement) x Event outcomes (loss of balance, apparent injury or symptoms etc.)

Other qualitative analysis methods reviewed provided support for determining risk factors from epidemiological literature, incorporating or adapting existing methods of qualitative analysis and the use of an expert panel to provide face validity (C. D. Burt, et al., 1999; David, et al., 2008; Ketola, et al., 2001).

4.2.3 Developing an understanding of the tackle

4.2.3.1 Movement goal

The goal of the tackle has been previously identified in the introduction to this thesis as differing depending on the perspective of the player involved. For the Tackler, the goal is well described by the tackle definition that has been used in this research, i.e. to stop the Ball-carrier and prevent gains in territory. The primary goal for the Ball-carrier must be for them to avoid the tackle contact completely in the first instance, while a secondary goal may be to commit as many defenders to attempting to impede their progress thus opening up space elsewhere on the field. Once in contact, the goal becomes to break free from the tackle contact if possible and then to retain possession of the ball for their team. Therefore, all factors which contribute to the success or failure of a tackle attempt and the effectiveness of any evasive technique that is employed by the Ball-carrier should be recorded by the protocol.

116 4.2.3.2 Critical features of tackling technique

The critical features of tackling technique that were identified from the coaching material and attending an ARU ‘smart rugby’ coaching session are summarised in Table 4.1. The information can be grouped according to the position the player should endeavour to achieve, the method of executing the tackle and notes following the tackle.

The coaching manuals that were reviewed during the development of the protocol did not identify tackling technique; however, the method advocated by the national governing bodies of Australia and New Zealand was the (active) ‘shoulder’ method where the Tackler uses the shoulder to tackle the Ball-carrier, grappling them with their arms and pushing or pulling them to the ground. Another method was described briefly in the Rugby Smart manual as the smother tackle. This method requires the Tackler to make contact above the waist and to wrap the Ball-carriers arms to prevent release of the ball (NZRU & ACC, 2005a). Three other methods were evaluated from observations made from video during earlier research (McIntosh, Savage, et al., 2005) and in preparation for this project. The first tackle occurred where the Tackler ‘held’ the Ball-carrier by grabbing their jersey and pulling them to the ground. This tackle will be referred to in the protocol as a ‘jersey tackle’. The second tackle was effected by the Tackler while falling or diving and using the hand to strike the Ball-carriers foot or lower limb and causing, or attempting to cause, the Ball-carrier to trip. The second tackle type will be referred to as an ‘ankle-tap’. The third tackle type was commonly observed in tackles where there was a size mismatch between the Ball-carrier and Tackler where a smaller Tackler executed a shoulder tackle in absence of leg drive, striking the Tackler about the waist, wrapping their arms around their body and dragging or pulling them to the ground. In this tackle the Ball-carrier was often observed to fall on the Tackler. This tackle will be referred to as a ‘passive shoulder tackle’. Additional tackle types that arise during analysis with the protocol or that are identified as an injury risk could be identified within an additional notes field and added to later versions of the protocol.

117 Ball-carrier Tackler Positioning x Evasion of the tackle impact x Achieve a low, crouched body prior to the - charging at the Tackler position, - altering running angle tackle x Back straight x Carry the ball in two hands x Shoulders above hips x Low body position x Eyes focused on the target area x Small steps prior to contact

During the x Attempt to break the tackle x Chin up, keep eyes on the target tackle contact - Side on position x Using arms to ‘grapple’ the - Drive the hard parts of the Ball-carrier body into the player x Leg drive (shoulder or hip) x Contact with the shoulder x Body before ball (Ball in trailing x Head to the side or behind the arm) Ball-carriers body x Good positioning of the feet. This will allow for extension of the lower limb (leg drive) x Wide step at contact x Maintain a low stable base x Chin up x eyes open x Small steps and push through After the tackle x Hug the ball to the chest and x Fall on top of the Ball-carrier squeeze hard with both hands when going to ground x Do not put an arm out to break your fall Table 4.1: Critical features of technique for the Ball-carrier and Tackler

Poor positioning of the Tackler prior to the tackle has been identified anecdotally as a reason for missed tackles (ARU, 2006a). Balance and stability were two important terms that were mentioned during this phase. The coaching material instruct that the Tackler should maintain ‘active feet’ by taking small steps as the Ball-carrier runs towards them and their body position should be low and crouched with the knees bent, tracking the Ball-carrier and the target zone at the waist. Wide base provides lateral stability and helps to stop Ball-carrier evasion. Both programs appear to recommend that the direction of the tackle is important and commented on the positioning of the Tackler in relation to the Ball-carrier. The ARU directed that the Tackler should not approach the Ball-carrier in direct opposition (from 180°) but from 15° to 45°, the NZRU recommended tackling on an angle ‘towards the inside’. As the Ball-carrier comes closer, the Tackler must try to get as close as possible before making the tackle. Achieving close proximity of the front foot to

118 the Ball-carrier’s base of support allows for a more effective shoulder hit and generation of force. The coaching material provided further guidance on the positioning of the arms, indicating that the Tackler’s elbows should be positioned anterior to the shoulder.

When entering the tackle contact, the Tackler should step forward towards the Ball- carrier and dip the torso to achieve low body height while maintaining the head up and spine straight. The Tackler should drive powerfully into contact with rapid extension of the lower limb at the knee and hips. The Tackler’s eyes should be open and focussed on their target and their chin should be up and not in contact with the chest. The initial contact point should be the Tackler’s anterior shoulder as it allows greater transfer of Tackler momentum to the Ball-carrier. To prevent potential injury to the cervical spine and concussion the Tacklers head should be beside the Ball-carriers body. The importance of the arms was also highlighted in both coaching manuals; the Tackler was instructed to wrap their arms around the Ball-carrier.

When confronted by a tackle, the initial aim of the Ball-carrier must be to evade the tackle contact completely and both programs indicated that the Ball-carrier should focus on evasion by holding the ball in two hands to increase the potential to offload the ball and over commit the Tackler. Potential evasion of the tackle could be further enhanced through powerful running and changing running angles during the approach towards a potential Tackler. The Ball-carrier should try to cross to the weaker shoulder and make the Tackler tackle across their line, not with it.

The terms balance and stability were again identified as outcomes of correct body positioning for the Ball-carrier prior to the tackle impact. The Ball-carrier is instructed to attain a ‘well balanced’ position from which they can attenuate the energy of the tackle and oppose the force of the Tackler. To achieve this position the Ball-carrier is instructed to attain a lower centre of gravity than the Ball-carrier, dropping their centre of mass by leaning forward, bending at the knees and hips while keeping the back straight. This was identified as a measure to improve stability. The Ball-carrier should take a powerful step towards the Tacklers leading

119 shoulder by making a wide step at contact. The purpose of this step was identified as to develop force and momentum while attempting to attain a front foot position close to Tacklers.

Within contact the coaching material referred to several observable features of posture. The Ball-carrier’s chin should be up and their eyes open to maintain awareness of the Tackler and to avoid head injury in the tackle. The Ball-carrier should try to achieve a smaller target and maintain a low stable base. The placement of the Ball-carrier’s feet was identified as an aspect of technique that could be used to both oppose the Tackler force and control the fall, i.e. if the line of the feet is perpendicular to the tackling players momentum then the player will have a poor support base and no way of countering the force of the tackle, he will be bundled over backwards. If the Ball-carrier’s feet are close to the alignment of the Tackler then the Ball-carrier will have a better support base to apply a reaction force from. The Ball-carrier should try to take small steps in contact to maintain the base of support and oppose the force applied by the Tackler and push through the tackle. The Ball-carrier should drive the hard parts of the body into the player through being in a side on position to the Tackler and protecting the ball by holding it in their training arm. When the Ball-carrier is held they should rotate the body to break through the tackle.

When going to ground maintaining possession of the ball was highlighted as the most important aspect followed by avoiding injury. The coaching material instructed the Ball-carrier to hold the ball in two hands and squeeze the ball, described in the coaching material as ‘hugging the ball’. The justification provided was that this motion causes the shoulders to be rounded which may help the Tackler to brace against the collision with the ground. The Ball-carrier is advised not to extend their arm towards the ground to break their fall. The concept of maintaining possession of the ball was emphasised within the coaching material. Because the possession is such a key feature for on field success it raises the possibility that a player might risk personal injury to maintain possession of the ball for their team or to score points.

120 The critical features can be grouped in the areas of awareness and visual tracking, posture and body positioning, and factors to prevent injury during a fall.

4.2.3.3 Match factors and weather and environmental considerations

Other aspects such as field position and players in support of the Ball-carrier and/or Tackler may also have an effect on the outcome of the tackle from a performance and injury perspective. For example, tackles which occur inside an opponent’s 22 metre zone may be more desperate attempts to stop a Ball-carrier and prevent a try from being scored. Tackles in this part of the field may involve more players and higher impact forces than tackles occurring in other parts of the field. The different playing positions also have different on field roles and workloads. While backs are likely to be involved in more passages of open play, characterised by higher running speeds, forwards are more likely to take the ball into contact more often. Position would provide useful information for the analysis.

The association between increased ground hardness and injury has been argued by Orchard (2002). Better match conditions are associated with favourable field and weather conditions and may result in increased match pace and player velocities. A higher match speed has been proposed to result in more forceful impacts (Orchard, 2002). The results of tackle injury research also suggest secondary collisions with the ground as an injury mechanism, particularly for upper limb injuries (Headey, et al., 2007). In these situations the firmness of the ground could be a risk factor for injury. Further, wet weather may cause a reduction in surface friction and a larger number of players falling when attempting to change directions, or more injuries as a result of poor body positioning at the tackle.

An important consideration when developing the protocol was how weather and field conditions can be evaluated accurately from video. Ground firmness presents a considerable difficulty for accurate assessment, but weather conditions, particularly precipitation, are relatively straight forward to evaluate. Lee and Garraway (2000) presented the difficulties in relying upon subjective assessment of the firmness of the playing surface, stating that such a judgement can only be used

121 to provide a broad impression. An indication of weather conditions can be obtained by determining if precipitation is apparent at the time of the tackle. Such a field can be dichotomous to improve reliability and this can be used to draw inferences about the condition of the playing surface. These inferences could be combined with more objective measurements, such as surface testing and meteorological records, in studies examining association between skill execution, injury risk and weather and pitch conditions. It is clearly not possible to assess the firmness of the ground from video, but it is possible for the analyst observing the event to comment on the presence of surface water on the ground or whether it is raining. This information could not be used to infer a link between injury and ground or weather conditions; it may provide a simple measure that would indicate further research is required.

4.2.3.4 Injury patterns and injury risk factors

The risk factors for tackle injury that have been identified in the literature were discussed in detail in section 3.4.4. Some of these risk factors have been confirmed in the review of critical features of technique (e.g. stability and awareness) and some may be assessed with singular categorical fields (e.g. Tackler engagement sequence, level of play and playing position) or a combination of fields (e.g. player speed, tackle direction, field position). Common injuries sustained during the tackle, such as joint sprains etc, were identified in section 3.4.2. Through the identification of injury patterns the likely mechanisms of injury were considered. For example, closed fractures and muscular haematomas are commonly caused by a force applied directly to the site of injury. In this case the body region struck on the injured player, the striking object/body part and the rater’s impression of the impact force may be sufficient to describe the injury event. Similarly with concussion, a description of the location of the impact may be sufficient to describe the aetiology. In other cases however, the cause of injury may not be attributed to a critical feature of the tackle, but to a more complex loading pattern of the joint or tissue. The main intrinsic and extrinsic risk factors for tackle injury were

122 considered according to the method proposed by Bahr and Krosshaug (2005). The results are presented in Figure 4.2.

Several authors have recommended that the tackle, particularly events that do not lead to injury, should be investigated (Bird, et al., 1998; Garraway, et al., 1999; McManus & Cross, 2004). A field describing an observable injury outcome such as medical treatment or suspected injury would assist in separating events where an injury occurred from those where there was no injury. In an earlier pilot study, this was achieved by identifying events where a player remained in contact on the ground following the tackle and appeared in pain or where a player received medical treatment following a tackle (McIntosh, Savage, et al., 2005). Similar field variables were selected for this analysis protocol and a third outcome: player leaves field; was also added to provide potential commentary on severity of injury.

Possible Intrinsic risk factors: Predisposed Susceptible Injury athlete athlete x Age x Body composition x Fitness x Strength Possible Extrinsic risk Inciting event: x Skill and co- factors: ordination x Shoe-surface interaction x Speed and momentum x Arousal x Ground hardness x Nature of contact x Confidence x Playing position x Number of Tacklers x Level of play x Direction of tackle x Field position origin x Muscle damage (workload) x Impact sequence of Protective factors Tacklers x Skill training x Subsequent ground x Strengthening programs contact x Proprioceptive training x Team mates in support programs

Figure 4.2: An analysis of factors resulting in an injury outcome arising from the tackle skill based on a model presented by Bahr and Krosshaug (2005)

123 4.2.4 Organising the information collected and refining the analysis protocol

The results of arranging the critical features of technique and other information collected during the development process using Haddon’s matrix is shown in Table 4.2. The table demonstrates that a number of fields in the analysis, such as speed, direction and body position, will be evaluated for both the Ball-carrier and Tackler.

Phase Ball-carrier Tackler Game environment x Speed x Speed x Ground conditions x Direction/alignment x Direction of travel x Weather conditions with opposition x Tackle drive preparation x Position on field Pre x Defensive line x Body positioning x Phase of play before tackle x Tackle preparation x Footwork x State of Game x Body height x Late target movement x Time in match x Ball carry method x Team mates in support x Proximity to try line x Impact square/oblique x Impact square/oblique x Foul play x Impact site x Impact with the target x Ground hardness x Body posture/Target area x Number of support size x Impact site players x Mobility in tackle x Team Mates in support x Arm mobility/options x Use of arms for passing the ball x Leg drive Tackle x Number of Tacklers x Ability to control tackle x Angle of additional x Head position Tacklers x Tackle from inside of x Opportunity to score opponent x Retention of ball x Ability to 'stop' x Evasion techniques opponent x Predisposition to x Predisposition to injury injury x Falling to present ball x Position on ground x Injury-stoppage correctly and (Above/under tackled x Injury-play on maintain possession player) x No Injury x Protection from injury x Secondary impact x Ball-carrier’s team during the fall x Team mates in support retains possession Post x Number of support x Involvement in x Tackler’s team gains players ruck/Maul possession tackle x Secondary impact x Obtain possession x next phase of play (ground etc) x Involvement in ruck/Maul x Maintain possession x Lose possession Table 4.2: Skill, environmental and match factors affecting the tackle (using Haddon’s matrix)

124 The results of the hierarchical analysis of the tackle are presented in Figure 4.3. Analysing the critical features technique for the tackle in this way assisted in both organising the information and for identifying observable components of skill. For example, the coaching material described balance as an important aspect of technique, but did not describe how a player might achieve balance or how it might be observed from video. The hierarchical analysis assisted in delineating how balance might be achieved and therefore informed how it might be observed.

Tackling

Force production/ Momentum absorption

Segment Running Balance Targeting Mass Contribution Speed

Space/ Stride Stride Eyes on Head clear of rate Length target Level defence

Lower body Back Arm contribution straight contribution

Stable base Step into Preparation & Grapple of support tackle positioning

Footing Knees bent Hips Flexed

Boot Ground Conditions type/studs (Wet/dry)

Figure 4.3: A hierarchical analysis of tackling from the perspective of the Tackler, based on the method of Hay & Reid (1988)

The tackle is a collision event and many of aspects of the skill are performed to produce or absorb force. It was therefore important that aspects of the skill

125 describing the collision were considered. The relationships between the tackle impact and the factors which determine the magnitude of the forces of that impact were analysed using the technique analysis method presented in Hay and Reid (1988). The force that is applied by a body is equal to the change in its momentum over time. Thus, objects with high momentum prior to a collision will be subjected to a more forceful impact. To this end, aspects of the tackle which would contribute to the development of momentum, such as running speed prior to the impact and the mass of the player are indicators of the momentum of a player. Other aspects of technique will also contribute to the magnitude of the tackle impact. A player may be stationary and still able to generate a forceful tackle through segmental summation of force (staged lower body extension, or leg drive).

4.2.5 First draft of the coder manual

An overview of the analysis process is presented in Figure 4.4. The protocol was separated into two levels of analysis described in section 4.1. Coding of a tackle indicates that the tackle met the studies tackle definition. In addition to the fields analysing technique, identifiers were included to indicate the time of the tackle, and provide a tackle reference number etc. The majority of the fields that were identified from the coaching material (critical features), epidemiological and biomechanical evaluations and environmental and match factors were included in the draft analysis protocol that was presented to the expert panel and research collaborators. The final draft protocol contained 90 fields (Figure 4.5). The fields were grouped according to event reference and match descriptors, technique, player awareness, biomechanical descriptors and environmental and ground.

126 Does the contact event meet No The event can’t be the studies definition for a coded tackle?

Yes

Can the Tackle No Analysis complete type be evaluated? The tackle should be counted only

Yes

Can the event be No coded accurately?

Yes

The event can be coded at the upper level

Does video of the No Analysis complete tackle allow extra Do not code the lower information to be level collected?

Yes

The lower level should be coded

Was there a No ground impact? Analysis Complete

Yes

Can the contact No accurately coded?

Yes

Code the ground impact

Coding Complete

Figure 4.4: An outline of the coding process (adapted from the IRB tackle study coder manual, Appendix A)

127 4.2.5.1 Event type and reference

The event is identified with a system generated tackle ID for indexing and game time assists in joining a tackle coding with video of the event. Text fields for additional notes, where the coder to address any aspect that was missed by the analysis, were included for the tackle and ground contact. Any observed injury to either player was also identified. The grade and level of play of the match provide important information about the players and patterns of play and may also provide inferences regarding skill level.

4.2.5.2 Match related event descriptors

The type of event or observed injury outcome was recorded according to the method that was used in pilot research (McIntosh, Savage, et al., 2005). Additional descriptors are whether the tackle also met the requirements of Law 15, the position of the tackle on the field and the type of tackle and number of Tacklers. Players are identified according to their jersey number to allow tackle codings to be linked with prospectively collected injury as appropriate and tackle legality would be assessed based on the referee’s decision. The protocol records the winner of possession subsequent to the tackle as well as any players in support of the Ball- carrier and any evasive action employed by the Ball-carrier to avoid the tackle. Match context is provided by identifying the phase of play before and after the tackle.

Event Type Analysis field Level Focus and Tackle ID Upper Identifier reference Game time Upper Identifier/global Can this tackle be coded in more Upper Global detail? Additional notes for each tackle Upper Global event Additional events for each tackle Lower Global pair Additional notes for ground contact Upper Global Injury to a player Lower Global Injury during ground impact Lower Global Level of play Upper Global Grade Upper Global

128 Match Analysis field Level Focus related Event type/outcome Upper Global event Did the tackle meet the definition Upper Global descriptors provided under Law 15 (tackle complete) If the event is not a Law 15 tackle Upper Global what occurred? Field half Upper Global Field corridor Upper Global Field aisle Upper Global Phase of play before Upper Global Phase of play after Upper Global Was the player tackled whilst Lower Global crossing the try line? Final score Upper Global Winning at the time of event Upper Global Tackle type Upper Global Is there a secondary impact Lower Tackler(s) between Tacklers? Tackle impact sequence Upper Global Number of Tacklers Upper Global Evasion (pre-contact) Lower Ball-carrier Evasion (contact) Lower Ball-carrier Ball-carrier’s position Upper Ball-carrier Tackler’s position Upper Tackler(s) Players in support Upper Retained ball for team Lower Global Final position of unit/tackle Lower Ball-carrier lifted by Tackler Lower Striking object Lower Tackler(s) or Ball-carrier Referee’s decision Upper Relative height Lower Global Relative mass Lower Global

Player Analysis field Level Focus technique Head and neck position Lower Tackler(s) or Ball-carrier Back straight Lower Tackler(s) or Ball-carrier Shoulders rounded Lower Ball-carrier Ball carry method Lower Ball-carrier Leg drive Lower Ball-carrier Knees bent: Lower Ball-carrier Small steps in contact Lower Ball-carrier Body height Lower Ball-carrier Arms grapple Lower Tackler(s) Tacklers head position in the tackle Lower Tackler(s) Control ball and prevent injury Lower Tackler(s) or Ball-carrier Sudden change of direction Lower Tackler(s) or Ball-carrier Tackler and Ball-carrier maintain Lower Global contact during fall

129 Player Analysis field Level Focus awareness Awareness of the Tackler Lower Ball-carrier Tackler is watching the Ball-carrier Lower Tackler(s)

Biomechanical Analysis field Level Focus event Force of impact Lower Global descriptors Biomechanical analysis possible Lower Global Feet alignment Lower Tackler(s) or Ball-carrier Base of support/stance width Lower Tackler(s) or Ball-carrier Feet preparation Lower Tackler(s) or Ball-carrier Is Tackler’s forward foot adjacent Lower Tackler to the Ball-carriers? Step into tackle Lower Tackler(s) or Ball-carrier Player speed Lower Tackler(s) or Ball-carrier Tackle direction Lower Ball-carrier Extends lower body (knees & hips) Lower Tackler(s) or Ball-carrier Knees bent Lower Tackler(s) or Ball-carrier Body region at point of impact for Lower Tackler(s) or Ball-carrier both players Direction of travel Lower Tackler(s) or Ball-carrier Body orientation of the player to Lower Tackler(s) or Ball-carrier direction of travel Direction after impact Lower Tackler(s) or Ball-carrier Body region struck during ground Lower Tackler(s) or Ball-carrier contact Side of fall Lower Tackler(s) or Ball-carrier Falling position Lower Tackler(s) or Ball-carrier Main region loaded Lower Tackler(s) or Ball-carrier Loading pattern of main region Lower Tackler(s) or Ball-carrier Range of motion exceeded Lower Tackler(s) or Ball-carrier Limb motion retarded Lower Tackler(s) or Ball-carrier Specific loading factors Lower Tackler(s) or Ball-carrier Did the Tackler contribute to the Lower Tackler(s) or Ball-carrier magnitude of load or excessive ROM Which player has the lower body Lower Tackler(s) or Ball-carrier position?

Weather Analysis field Level Focus Ground dry Upper Global Raining Upper Global

Figure 4.5: Fields in the tackle analysis protocol

4.2.5.3 Player technique and awareness

Skill execution for both the Tackler and Ball-carrier was assessed in the protocol using a number of fields to evaluate critical features of technique including body posture and awareness. Body position fields were assessed for individual joints and

130 comparatively for the full body. Awareness of an opponent, or player tracking, has been measured in other qualitative studies by assessing whether the player had their eyes on their opponent (Andersen, et al., 2003) and was therefore considered satisfactory for this study. Sudden changes of direction prior to the tackle that might place an opponent in a less desirable position were evaluated by recording late changes in direction and maintaining momentum in that tackle was assessed by indicating whether the player used small steps in contact. The use of the Tackler’s arms to grapple the Ball-carrier was also evaluated.

4.2.5.4 Biomechanical event descriptors

A number of observable aspects of skill arising from the various methods that were used to arrange the information, such as the hierarchical analysis of critical features of technique and Haddon’s matrix, were included in the protocol. Balance and stability were identified as two important aspects of preparing for the tackle for both the Ball-carrier and Tackler. For the purposes of this research these terms were deemed to represent the ability of the player to maintain a stable base. Feet preparation, feet alignment and stance width were identified as suitable aspects which could be observed from the video and used to evaluate aspects of stability of the players. Stepping into the tackle, extension of the lower body and player speed and direction of travel were included to evaluate the player’s momentum carried into the tackle and the development of momentum during the tackle contact. Assessment of a number of injury risk factors was also included in the analysis protocol. The field for specific loading pattern identified aspects such as:

x Fall onto head/neck x Fall onto thorax/shoulder x Fall onto back/buttocks x Lifted and turned x Fall onto outstretched limb x Foot/lower limb locked upper body twisted resulting in knee loading

131 Other fields that described loading pattern according to the mode of loading (stretching, impact or crush) and the body region or part that was affected were also included in the analysis protocol.

4.2.5.5 Match and weather conditions

Match and weather conditions were recorded in the protocol using rudimentary fields to assess whether the ground was dry during the match and if it was raining so that any effect on the tackle event can be analysed.

4.3 Expert Meeting

The feedback that was received during the meeting with the panel of experts was generally positive. All feedback that was received related to the panels opinion of the ‘validity’ of the fields in the protocol and not to whether the protocol could be realistically applied to evaluate the targeted aspect of skill.

The main point that was communicated by the panel was that player that controls the tackle wins the ball. If the Tackler can prevent the Ball-carrier from off-loading or turning in the tackle then his team will win the ball. This point was made during the discussion about the Ball-carrier risking personal injury to maintain possession of the ball for their team. The panel noted that control of the tackle was well described by several of the analysis fields. The panel concurred with the importance of associating playing experience with injury aetiology where possible and were satisfied that this could be measured through recording the level of play in terms of age group and grade or, more preferably, by determining the duration of a players rugby experience through referring to registration databases. The later method would be more accurate, but would also be more demanding than rudimentary age level and grade of play measures. However, it would be possible through the field recording players’ jersey numbers, and provided with access to accurate match team sheets, to identify participants and their positions from the game corresponding to the video and access to the registration database of the

132 governing body. The expert panel considered that it was important for the analysis to be able to correlate specific injuries, such as catastrophic spinal injuries or serious knee injuries, with the rate of occurrence of tackle type and were satisfied with the additional tackle types (smother, ankle-tap, jersey and passive shoulder) that were provided in the protocol. The panel commented on a relationship between tackle type and tackle efficacy, noting that arm contact alone did not have as much momentum as a shoulder tackle. Situations where tackle choice was possibly the cause of poor player positioning, as distinct from where the arm tackle was used out of necessity, should be described. Once again the panel was satisfied that this was addressed by the direction of tackle origin, the respective speed of the players, feet preparation and leg drive.

A discussion point during the presentation was the development of momentum or energy within the tackle. The expert panel confirmed the perspective of the coaching material that momentum in the tackle was developed through attaining a foot position close to the opponent’s base of support, maintaining small steps in contact for the Ball-carrier or a narrow base for the Tackler and the importance of leg drive. While an acute angle of approach had been identified in the literature for the Tackler, the panel stated that the Ball-carrier should also approach the Tackler from 15-30o off centre. It is important for both players to drive the hard parts of the body into the opponent to maximise the impact force. It was therefore also important for the Ball-carrier to maintain a small body shape. The panel also noted that the body region struck during the tackle contact provided useful information and noted that, at that time, junior players were taught to tackle with the anterior shoulder to protect the AC joint from injury.

Other aspects of the protocol that the panel commented on were the body size of the players involved and the time of the tackle in the match. When discussing the relative size of the players in the tackle, a member of the panel hypothesised that tall players were more likely to be injured because they have longer levers, noting that the relative size of the players involved in the tackle to each other may provide a useful comparison. When discussing the time of injury in the match, one of the

133 coaches presented their personal opinion regarding injury risk. The coach noted that in their experience tackle injuries occur early in the half, players have warmed up physically but haven’t gotten used to tackling. The ‘match time’ field had been incorporated in the protocol as an index of the tackle event. An additional utilisation of the field was as a dependent variable for injury analysis in response to authors hypothesising fatigue as the reason for elevated injury rates in the third quarter of matches, before players are substituted (Bathgate, et al., 2002).

The presentation of the protocol to the expert panel served as a valuable process where the structure and content of the analysis where validated. While no major changes were made as a result of the presentation, several ideas for the direction of subsequent analyses with the protocol were discussed.

4.4 Research Collaboration

The final draft of the tackle protocol was presented at a meeting between the research groups of UNSW and the RFU in Sydney, where the independently prepared protocols of both groups were compared. The definition of a tackle was accepted without alteration. Common fields to both protocols were identified and the merit of including of fields that were not common to both was discussed. No fields were deleted as a result of these discussions. Fields were either added unchanged or merged with existing fields in the respective protocol. The 90 items presented in Figure 4.5 expanded to 107. The field variables were scrutinised for each field and the definitions were discussed according to the intended application. Some minor alterations to field variables were made and, in a small number of cases, field variables assessing a target in one protocol were used in preference to those that were used in the other protocol to assess the same target. An ‘unknown’ field variable was added to all fields. At the conclusion of the meeting the protocol agreed by the research groups was written as a formal definitions document and a coder manual was created.

134 4.5 Summary

The development process for the tackle protocol which has been outlined in this chapter was made within the framework of a systematic and repeatable method for creating a qualitative movement analysis method. The final draft protocol contained 107 fields and was separated into two levels of analysis; an upper level consisting of generic tackle descriptors, such as type of tackle and position on the field and a lower level describing specific technique attributes of the players involved. This division allows the protocol to be applied in full to events where good vision is available while also collecting valuable descriptive data for important fields when some or the majority of aspects of the skill are obscured. In addition to the fields analysing technique and assessing potential injury risk factors, a number of identifiers were included to indicate the time of the tackle and provide a tackle reference number etc. The final draft protocol was incorporated into a coder manual for reliability testing (appendix A).

135

136 CHAPTER FIVE

TESTING RELIABILITY OF THE TACKLE ANALYSIS

PROTOCOL

The main limitations of previous sport science research utilising qualitative analysis methods have been the absence of a detailed description of the development of the protocol and assessment of the protocol’s reliability. This research has attempted to provide a detailed description of the process used to develop the analysis protocol, which provides justification for the inclusion of specific fields and assists in establishing the reliability and validity of the protocol. The analysis protocol that was described in the preceding chapter was developed by identifying skill specific and intrinsic and extrinsic variables that influence performance through the application of existing biomechanical and epidemiological frameworks. This chapter will present the results of reliability testing of the tackle analysis protocol that was described in Chapter Four. The full protocol has been included in appendix A as the coder manual that was provided to participants during this testing.

5.1 Methods

Subsequent to the development of the analysis protocol, reliability was tested in an IRR study. Ethics approval for the study was obtained from the University of New South Wales Human Research Ethics Committee (reference 08/2010/30).

5.1.1 Participants and Task

Participants in this study were members of the biomechanics and rugby safety research group, school of risk and safety sciences, UNSW and from staff at the ARU and the RFU (UK). An email invitation consisting of a brief description of the purpose of the study and participation expectations was distributed to potential raters within these organisations, inviting those who were familiar with the aim of

137 the game, terminology, and who had a basic understanding of the rules of rugby, to express interest in participating. Nine (9) individuals responded to the email and all nine agreed to participate in the first IRR study. Four of the respondents were based in Australia and five were based in the United Kingdom (UK). All participants were familiar with rugby union, seven of the nine participants had playing experience, and all had a basic understanding of the rules.

The large number of fields and field variables presented difficulties in the ease of application of the tackle analysis protocol. A coding/data collection tool that facilitated the storage of all 107 fields in the analysis was required. Prior to developing the analysis tool the following objectives were identified:

x The tool must be uncomplicated and easy to use by any person with suitable training (in the use of the protocol) x The tool must be easy to distribute for use on any PC x The tool must provide easy and accurate extraction of results for statistical analysis

A number of commercially available video analysis tools, including Snapper (Webbsoft technologies), Dartfish and SportsCode were reviewed for reliability testing and were eliminated because of cost and/or insufficient hardware. Therefore, to fulfil the objectives for the analysis tool, a tackle workbook was created for use in Microsoft Excel (2003). The workbook allowed for additional functionality through a custom made visual basic subroutine. To ensure accuracy and continuity in terminology, the responses for each field were limited to the field variable list. A graphical user interface to record and save the values for fields and field variables of the tackle analysis protocol was developed programmed using Visual Basic (Appendix B).

Instructions were provided to the participants in the coder manual for the study (Appendix A, page 6-A). A CD ROM of study materials was prepared for all study participants. It included twenty video clips of tackle events, two videos of match play (of five minutes duration), the tackle workbook and a copy of the coding manual in Portable Document File (PDF) format. The twenty video clips were

138 numbered 1 through 20. The five minute match videos were numbered one and two and both contained a video counter code for event indexing. Preliminary evaluation of analysis using the full protocol revealed that to complete an analysis of one tackle required between 30 and 45 minutes. Therefore, to reduce the time expectations upon the research participants a minimum requirement was set, participants were asked to use the tackle workbook to code video clips one through to ten and any events which they identified as tackles according to the study definition in the first five minute passage of play. If time permitted, participants were then asked to code the remaining ten video clips (numbered 11 to 20), and finally the second five minute passage of play. Codings from both the tackle video clips and tackles identified by the participants from the passages of play were used to test reliability of the protocol. The passages of play were used to test the reliability of the tackle definition. All video footage was coded by an ‘expert’ coder who had been involved in the development of the protocol.

5.1.2 Training

To maintain coder objectivity and enhance reliability of the codings, all participants were provided with direction on the application of the protocol through attending an instructional seminar. The seminar provided the participants with:

x An overview of the analysis process x Direction on the application of the analysis fields x A strong reminder that anything that could not be evaluated with certainty should be coded as ‘unsure’

The protocol was presented and explained to all participants using a power point presentation and the coder manual (appendix A) and the CD ROM containing study materials (video of 20 tackles and four five minute passages of play) were distributed during the training session. During the seminar, time was allotted for general discussion to address any uncertainty regarding the application of the protocol and to clarify terms used. To cater for participant groups in two different geographical locations two instructional seminars were conducted. One seminar

139 was presented to the four participants that were based in Australia and the second was presented to all participants in the UK. The content of the two seminars and the material provided to participants were identical. However, because of logistics and costs of travelling to the UK, the seminars were not presented by the same instructor. The UK seminar was presented by a representative of the RFU with whom the masters candidate was in regular telephone and email contact.

5.1.3 Measurement of agreement

Once the tackle workbooks were returned, the data were compiled to assess agreement. Reliability and methods for assessing agreement were discussed in sections 3.6 and 3.7 of the literature review. Because this research used multiple raters assessing a target with primarily nominal field variables which were not dichotomous, agreement between raters in all fields was evaluated using the percentage of agreement. The formula for percentage agreement was presented on page 104 of section 3.7. A worked example of the calculation is presented in appendix C. Intraclass Correlation Coefficient (ICC) was assessed using a two way mixed effects model. ICC was used as a supplementary measure of agreement when evaluating agreement for identifying tackles according to the study definition. Agreement was interpreted according to the arbitrary values of Landis and Koch (1977). However because percentage of agreement cannot be negative, and to address concerns about the method not accounting for chance, the scale was modified for the purposes of assessing percentage of agreement (Table 5.1).

Kappa Statistic Strength of Agreement 0.11-0.30 Poor 0.31-0.50 Fair 0.51-0.70 Moderate 0.71-0.90 Substantial 0.91-1.00 Almost Perfect Table 5.1: An arbitrary scale for assessing percentage agreement, modified from Landis and Koch (1977)

Because many of the results in the chapters assessing agreement have been presented as percentages (e.g. percentage of change in agreement between studies

140 etc.), the percentage of agreement will be presented as an agreement rate where 0.8 is equivalent to agreement of 80%.

5.2 Results

Of the nine participants in the first inter rater reliability study (IRR1), six completed the minimum task required (videos 1 to 10 and all events from one 5 minute passage of play, 5mins1.avi). A further two participants completed coding for the individual video clips 1 to 10 only. One participant coded only 7 tackles and was excluded from the analysis. Because the expert coder had specific insight into the desired application of the tackle analysis protocol, their codings were also included in the analysis. Therefore, nine participants coded all videos one to ten and seven participants coded all events that they identified as tackles in one five minute passage of play. There were 18 tackles (inc. Three sequential tackles) in the five minute passage of play for a total of 30 tackles to be evaluated for the study.

An overview of the analysis process is presented in Figure 5.1, identifying the number of fields and mean agreement rate for each analysis level or section (e.g. upper level, lower level etc.). Ten of the 107 fields in the analysis protocol were designated as record identifiers which were generated by automated processes. Agreement was assessed in the remaining 97 fields. The mean agreement rate amongst participants in the first IRR study, and for all of the fields of the tackle analysis protocol, was 0.61. The results of IRR1 will be presented for the upper level and for tackle and ground contact fields for the Ball-carrier and Tackler.

5.2.1 Tackle definition

The average percentage of agreement between participants for identifying tackles according to the study’s tackle definition was 73% and the average measure ICC was 0.75 (95% CI = 0.57 to 0.87). Of the 18 tackle events in the five minute passage of play, one coder was able to correctly identify 16 tackles (94%). Two coders correctly identified 13 (76%) and two coders correctly identified 11 (64%). When ‘missed tackles’ were excluded from the comparison, the agreement rate increased to 0.80.

141 Tackle analysis protocol Number of fields: 97 Mean agreement rate: 0.61

Upper level analysis Lower level analysis Generic Description of the tackle Detailed analysis of the tackle Number of fields: 27 and ground contact for the ball Mean agreement rate: 0.70 carrier and Tackler Number of fields: 70 Mean agreement rate: 0.58

Tackle contact analysis Tackle contact analysis for the Ball carrier for the Tackler Number of fields: 22 Number of fields: 22 Mean agreement rate: 0.59 Mean agreement rate: 0.58

Ground contact analysis Ground contact analysis for the Ball carrier for the Tackler Number of fields: 14 Number of fields: 12 Mean agreement rate: 0.54 Mean agreement rate: 0.59

Figure 5.1: An overview of the number of fields and mean agreement rate for each level of the analysis

5.2.2 The upper level

The proportion of agreement in upper level fields is displayed in Table 5.2. The mean agreement rate for all upper level fields was 0.70. There was a wide variation in the agreements rates observed, and this was reflected in the Standard Deviation from the mean for the upper level analysis fields (SD = 0.18). The three fields with the highest observed agreement rates were event type, whether it was raining

142 and if the Ball-carrier was attempting to score a try. Agreement rates of over 0.80 were obtained for three important event identifiers: Event type (0.90); the number of Tacklers involved in the tackle (0.87); and whether the tackle was complete (0.81). A high agreement rate was also returned for whether the event could be coded further (0.81).

Upper level analysis fields Field Name Agreement Event type 0.90* Field half 0.73 Field corridor 0.69 Field aisle 0.66 Ball-carrier jersey number/position 0.66 Ball-carrier team 0.53 Grade N/A Tackler team 0.52 Relative height 0.48 Relative mass 0.48 Ground dry 0.73 Raining 0.95 Ball-carrier team winning N/A Ball-carrier attempting to score 0.96 Phase of play before 0.49 Tackle type 0.46* Was the tackle complete? 0.81 Why was the tackle not complete? 0.37 Impact/engagement sequence 0.76 Phase of play after 0.68 Impact force 0.63 Referees decision 0.87 Ball outcome 0.63 Number of Tacklers 0.87 Further coding 0.81 Evasion technique 0.60 Tackle bust method 0.42 Ball-carrier team retains ball 0.81 Table 5.2: Agreement rates in Upper level analysis fields for IRR1 *Agreement rates changed when similar variables were grouped

Event descriptors, including assessment of it was raining at the time of the tackle, the referee’s decision, retention of possession of the ball and whether the player

143 was attempting to score a try also had high agreement rates between 0.80 and 1. The sequence of Tackler engagement with the Ball-carrier had an agreement rate of 0.76 amongst the participants. Within this field, agreement for one on one tackles was 0.90, while the participants had difficulty discerning the sequence of engagement in multiple Tackler events. Simultaneous and sequential tackles had lower agreement rate (0.47 and 0.17 respectively). The field position descriptors (field half, aisle and corridor) had good agreement (0.66 to 0.73) and agreement between participants when evaluating impact force and the appearance of ground conditions also produced good agreement (0.63 and 0.73 respectively).

The participants had more difficulty in determining the phase of play before the tackle than after the tackle and there was also lower agreement in identifying which teams the players (both Ball-carrier and Tackler) were representing and in evaluating the height and weight of the players involved. The agreement rate for the tackle type (0.46) was below the rate observed for many fields in IRR1 and under the average agreement rate for all upper level fields. Agreement rates for individual tackle types are presented in Table 5.3. The highest agreement rates were observed for the active shoulder tackle, arm tackle and ankle-tap. When the two shoulder tackle types, active and passive, were combined the observed agreement rate increased to 0.72.

Tackle type Agreement rate Active shoulder 0.58 Passive shoulder 0.37 Subtotal – 0.72 Shoulder tackles Jersey 0.46 Ankle-tap 0.47 Smother / hug 0.32 Arm (short/long) 0.57 Unsure 0 Total 0.46 (0.59*) Table 5.3: Observed agreement rates for variables in the tackle type field of IRR1 *Total agreement rate when active & passive shoulder tackles were grouped

144 5.2.3 The lower level

The lower level analysis consists of fields describing skill execution and injury risk during the tackle impact. The lower level analysis is completed for each Ball- carrier and Tackler pair and can be further divided into fields describing the characteristics of tackle contact and fields evaluating ground contact characteristics. The lower level therefore consists of four distinct analysis compartments which can be used to describe the tackle. The results will be presented according to these compartments.

5.2.3.1 The Ball-carrier: assessment of contact characteristics

The results for lower level analysis for tackle contact fields for the Ball-carrier are presented in Table 5.4. The lower level analysis resulted in a mean agreement rate of 0.59 (SD = 0.14). The three highest agreement rates were observed in fields evaluating whether the Ball-carrier was lifted during the tackle, the Ball-carrier’s awareness of the Tackler and their body orientation to the direction of travel. The lowest rate of agreement was observed for the evaluation of the direction of movement of the Ball-carrier after the tackle impact (0.32).

Generally, lower agreement rates were observed in fields assessing body postures and regions involved in contact. The body region struck during the tackle had a poor agreement rate (0.33) and agreement rates for fields assessing body position, such as those evaluating the extension of the back or flexion of the knees, varied from 0.45 to 0.76. The highest agreement rates were returned for positioning of the feet and the orientation of the upper body to the direction of travel. The lowest agreement rate for a fields assessing body position was for the field assessing the body height of the Ball-carrier when entering the tackle impact. This field was assessed on a three item nominal scale (high/low/unsure). The agreement for body region, which consisted of thirteen variables in the protocol that was tested, improved marginally to 0.45 when similar body regions were grouped (e.g. Head and neck; shoulder and upper arm; and chest, back and abdomen as torso, etc.).

145 Grouping of variables within other fields of the protocol also generally resulted in an increase in the observed agreement rate.

Ball-carrier analysis fields

Field Name Agreement Aware of Tackler 0.82 Team mates in support 0.73 Back straight 0.62 Shoulders rounded 0.51 Ball carry method 0.55 Feet alignment 0.72 Stance width 0.37 Steps into tackle 0.63 Steps to base 0.61 Knees bent 0.56 Small steps in contact 0.56 Body region struck 0.33* Tackle direction 0.69 Head and neck position 0.68 Speed 0.56 Direction of travel 0.59 Body orientation 0.76 Body height 0.41 Direction after tackle 0.32 Lifted in tackle 0.90 Table 5.4: Agreement rates in fields evaluating the tackle impact for the Ball- carrier *Agreement rates changed when similar variables were grouped

The observed agreement rates for fields using rugby specific terminology varied. The highest agreement rate was observed in the field evaluating whether the Ball- carrier was supported by team mates (0.73). The fields describing the evasion technique that was employed by the Ball-carrier or the method of breaking free from engagement with the Tackler had agreement rates of 0.60 and 0.42 respectively. The ball carry method and ability of the Ball-carrier to maintain momentum throughout the tackle (by taking small steps in contact) had similar agreement rates.

146 There was a trend for agreement rates in descriptive and physical principle fields, such as those evaluating directions, speed, awareness and player identification, to be slightly higher than fields evaluating posture and rugby union amongst the participants in this study. The three fields evaluating directional attributes demonstrated different levels of agreement. Evaluating the direction of travel after a tackle had the lowest agreement rate (0.32) while a higher rate of agreement was observed when evaluating the Ball-carriers direction of travel prior to the tackle (0.59). A similar rate of agreement was observed for the players speed (0.56) and jersey number. The highest agreement rate was observed for evaluating the direction of the tackle origin with respect to the Ball-carrier (0.69).

5.2.3.2 The Tackler: assessment of contact characteristics

The results for lower level analysis fields for tackle contact for the Tackler are presented in Table 5.5. The mean agreement rate for all fields was 0.58. The three fields with the highest observed rates of agreement were for the Tackler tracking of the Ball-carrier (0.92), whether there was a secondary impact with another Tackler (0.84) and arms grapple (0.74). The lowest agreement rate was observed for evaluation of the direction of travel and the direction after the tackle (0.24 and 0.28 respectively). Once again a wide variation in the agreement rates for descriptive and postural fields was observed.

While the observed agreement rates for Tackler tracking of the Ball-carrier and secondary impact with another Tackler were high, other descriptive fields evaluating physical principles had lower agreement rates. Both directional fields, which were evaluated using a cardinal system applied globally from the Ball- carriers perspective, had agreement rates below 0.30. The agreement rate for player speed was 0.47, below the mean agreement for this section of the protocol. The Tackler’s orientation to the direction of travel and identification of the Tacklers playing position (jersey number) were above the average agreement rate for the section and 50%.

147 Tackler analysis fields

Field name Agreement Eyes on the Ball-carrier 0.92 Tackler jersey number/position 0.69 Back straight 0.63 Lower position than Ball-carrier 0.70 Arms grapple Ball-carrier 0.74 Feet alignment 0.69 Stance width 0.40 Steps into tackle 0.61 Steps to base 0.58 Knees bent 0.62 Small steps in contact 0.56 Feet preparation 0.39 Extends lower body 0.43 Body region struck 0.48* Head and neck position 0.55 Speed 0.47 Direction 0.24 Body orientation to direction of travel 0.72 Body height/posture 0.40 Direction after the tackle 0.28 Impact with other Tackler 0.84 Head position 0.46 Table 5.5: Agreement rates in fields evaluating the tackle impact for the Tackler *Agreement rates changed when similar variables were grouped

The results of fields evaluating posture and body regions were similar to what was observed for the Ball-carrier. The agreement rate for body region struck was 0.48. In fifteen of the thirty tackles that were presented to the participants, the ratings were split when identifying whether the main region struck in the tackle impact was the shoulder or the chest. Similar disagreement occurred in several tackles for the upper limb and shoulder and between the chest and neck. When the thirteen variables in the body region struck field were grouped (head and neck, chest, back and abdomen, shoulder and upper limb, hips and thigh, knee, lower leg) the agreement rate improved to 0.77. Agreement for fields assessing the level of flexion and extension of the spine, knees and head and neck were 0.63, 0.62 and 0.55 and were similar for the results for corresponding fields for the Ball-carrier.

148 Interestingly, the height of the player and approximation of the player’s stance width, two fields with agreement rates of approximately 0.40 for the Ball-carrier also demonstrated low agreement when evaluated for the Tackler (both 0.40).

The field evaluating the Tacklers use of their arms to grapple or hold the Ball- carrier, assessed on a three item nominal scale, produced a moderately high agreement rate (0.76). Lower agreement was observed for agreement in the fields evaluating the Tacklers head position and feet preparation. The Tacklers head position was evaluated with reference to the Ball-carrier (e.g. beside, above, below the Ball-carrier) while feet preparation was also evaluated on a four item nominal scale (no movement, small steps, wide steps, unsure).

5.2.4 Ground contact

The results of the lower level ground contact analysis, or the collision sustained by either the Ball-carrier and Tackler with a stationary object after the primary tackle collision, will be presented in this section for the Ball-carrier and Tackler separately.

5.2.4.1 The Ball-carrier: assessment of secondary contact or ground contact

The results of the ground contact analysis for the Ball-carrier are presented in Table 5.6. The mean agreement rate for all fields was 0.54. The highest agreement rates were observed for fields confirming that a ground or secondary impact (with a stationary object) had occurred and identify the nature of the object (i.e. ground, signboard, goalpost etc.) Other fields where agreement rates of 0.60 and above were recorded were the side of the body affected during the fall or ground contact (left or right), the position of the Tackler with respect to the Ball-carrier following the tackle, if a joint range of motion was exceeded and the body position during the fall. The result for body position is in contrast to the agreement rate obtained in similar fields during tackle contact for both the Ball-carrier and Tackler where agreement of 0.40 was observed.

149 With the exception of the field evaluating whether joint range of motion was exceeded, other fields assessing the loading patterns applied to the body during the secondary impact had agreement rates below 0.45. All of these fields were evaluated on a three item nominal scale (yes, no, unsure). Similar to the results for main tackle impact, the body region struck during the secondary impact had an agreement rate of 0.31. A field intended to identify a body region subject to a specific loading pattern also had a similar agreement rate (0.41). Once again, the agreement rate for the body region struck was observed to increase (0.43) when adjacent body regions were grouped.

Ball-carrier ground contact analysis fields Field name Agreement Ground contact 0.77 Striking object 1.00 Body region struck 0.31* Final position of Ball-carrier after fall 0.61 Side of the body loaded during fall 0.73 Body region loaded 0.41 Injured with ground impact 0.54 Range of motion exceeded during fall 0.60 Limb motion retarded during fall 0.44 Loading pattern at ground contact 0.43 Exposure to specific risk factors 0.33 Body position/posture during fall 0.60 Controls fall 0.46 Tackler contributes to load during fall 0.59 Table 5.6: Agreement rates in fields evaluating ground contact characteristics for the Ball-carrier *Agreement rate increased to 0.43 when similar variables were grouped

5.2.4.2 The Tackler: assessment of secondary contact or ground contact

The results of the ground contact analysis for the Tackler are presented in Table 5.7. The mean agreement rate for all fields was 0.59. Similar to observations that

150 have been noted for the Ball-carrier, the highest agreement rates were recorded in fields confirming that ground contact occurred and identifying the nature of object that was struck during the secondary impact. The body posture of the Tackler also had a high agreement rate above 0.90, which was higher than the comparable field for the Ball-carrier. Both of these fields, evaluating posture of the Ball-carrier or Tackler while falling, resulted in higher agreement than comparable fields evaluating the posture of the player when standing during the tackle contact. The lowest agreement rates were observed in fields requiring the participants to identify body regions. This result contributes to the consistent trend of low agreement that is apparent in similar fields within other areas of the analysis protocol.

Tackler ground contact analysis fields Field name Agreement Ground contact 0.72 Striking object 0.89 Body region struck 0.30 Final position of the Tackler after fall 0.54 Side of body loaded during fall 0.64 Body region loaded 0.30 Injured with ground impact 0.68 Range of motion exceeded during fall 0.62 Limb motion retarded during fall 0.70 Loading pattern at ground contact 0.43 Exposure to specific risk factors 0.47 Body position/posture during fall 0.91 Table 5.7: Agreement rates in fields evaluating ground contact for the Tackler

The fields evaluating the loading pattern applied to the body during the secondary impact and the presence specific risk factors such as fall to the head and neck or a fall to an outstretched limb had agreement rates of 0.43 and 0.47 respectively. Both of these fields were analysed on a multiple item nominal scale. Agreement amongst the participants when evaluating the final position of the Tackler after the secondary impact and their falling posture was 0.48 and 0.50 respectively. These items were analysed on a three item nominal scale.

151 5.3 Changes to the Analysis Protocol and Discussion

Following the completion of the first IRR study, the results were discussed at a meeting with an expert panel. The expert panel consisted of a biomechanist with extensive epidemiological experience, an epidemiologist, a medical doctor a research assistant and the master’s candidate. During this meeting the results of IRR1 for every field in the protocol and the definitions that were provided to participants in the coding manual for the study were reviewed. The videos where disagreement occurred were reviewed to identify potential reasons for disagreement. The results of agreement for tackle type and other fields was lower than expected and feedback was received from one of the study participants that had been difficult to know when to evaluate specific fields. Several trends were apparent from the agreement results. Lower percentage of agreement was observed for fields where participants were asked to identify the body region struck during the contact and fields that were developed to evaluate loading patterns that were experienced by a player during ground contact.

Confusion over the timing of analysis for some fields was a main focus of the meeting and the review of agreement results. After reviewing the results, it was suggested that agreement in many of the fields could be improved by defining a temporal assessment period with respect to a tackle event reference time (T0). Because the central focus of the tackle analysis was the tackle contact, there was consensus that T0 should coincide with the first observed contact between the Ball- carrier and Tackler, i.e. the commencement of the tackle. This was determined to be affected by the type of tackle and thus tackle types. The type of tackle could be triangulated using the body region struck e.g. in a shoulder tackle the shoulder should be the body region struck while for an ankle-tap the forearm and hand should be the body region struck. All fields in the protocol were reviewed to determine when evaluation should occur with reference to the T0.

The ‘event type’ field was an important field for the description of injury events. Similar fields had been used for the analysis of injury risk factors in other sports and improved agreement for medical events was sought (Andersen, et al., 2003;

152 Koh & Watkinson, 2002). The percentage of agreement for event type was generally good (91%). However, in the sample of tackles that were used in IRR1 there were few medical events and this may have influenced the results. Of the twenty eight tackle events that could be coded, only four were medical events (14%). Percentage of agreement for medical events (knock down, 42%, and medical aid sought, 61%) was lower than the generic tackle event (95%) where no ‘injury’ was observed. The main difference between the ‘knockdown’ and ‘medical aid sought’ field variables that were used in IRR1 was that for the ‘knockdown’ event the player appeared in discomfort and did not return to their feet immediately, while for the ‘medical aid’ event the player must receive medical attention on the field as a result of the tackle. The definition for knockdown, while similar to a definition used by Koh and Watkinson (2002) where the athlete appeared to be dazed or unsteady, is clearly subjective. To strengthen the definition in this field, the knockdown variable was clarified by referring to visual cues in the field definition and providing guidance for the duration that a player was to remain on the ground before a knock down event was recorded. Previous research had used definitions ranging from standing down following an eight count in Taekwondo (Koh & Watkinson, 2002) to more than fifteen seconds in soccer (Andersen, et al., 2003). At least five seconds was adjudged to be sufficiently long enough for the purposes of this analysis protocol.

Where possible, definitions for rugby specific fields in the analysis protocol were aligned with definitions provided in the rule book. The phase of play before and after is an example of a field where this occurred. Agreement for the phase of play before the tackle was lower than mean agreement observed for the protocol (0.49). Within this field there was disagreement when evaluating between rucks, tackles and open play. The field variables where adjusted to reflect the laws, where possible. In one case, open play, visible restrictions (Ball-carrier runs 5m or more or the ball travels through three or more Ball-carriers before the tackle) were added to the definition to assist the observer in making an accurate evaluation of the field.

153 The body region struck during contact generally presented lower agreement than other fields that were tested in IRR1. This observation was true for both the Ball- carrier and Tackler and for during the main tackle impact or any subsequent (or ground) impact. A review of the coding manual for IRR1 determined that the body regions had been named but not defined. Therefore inter-participant assessment of these named regions may have differed and contributed to the lower agreement rates. It was determined that a more stringent definition of body region was required. All body regions were defined according to anatomical boundaries. To account for situations where the body region struck during the main tackle contact was obscured two fields were added, an unsure fully obscured variable and an unsure upper body variable. To account for the triangulation of tackle type an additional field variable which was associated with both the jersey and ankle-tap tackle types, forearm and hand, was added to provide additional detail and strengthen triangulation.

There was obvious difficulty in defining the timing for the body region struck during ground contact. There was concern that by only identifying the first body region to collide with the ground other important information about regions loaded during the secondary impact could be lost. To address this issue it was resolved that coders should be able to identify three body regions struck during the impact in order from when they make contact. Torso and abdomen and back changed to anterior trunk and posterior trunk.

Evaluation of joint position had mixed results in the first IRR study and other authors have noted difficulty in obtaining accurate and valid assessment amongst expert raters for joint magnitudes and some defined ranges (Krosshaug, et al., 2007; McAtamney & Nigel Corlett, 1993). While precise estimations of joint range weren’t required in this study, it was proposed that a better frame of reference was required to assist observers to make accurate assessments and improve agreement in these fields. Estimation of joint angles was therefore provided a neutral reference and the dichotomous field evaluating if a players knees were bent was changed to ask if the players knees straight. When assessing the height of the

154 players in the tackle (whether a player obtained a lower body position in relation to their opponent) the lower body position taken from relative reference of the shoulders. No changes were made to the fields assessing relative height and mass of the Ball-carrier to the Tackler.

Fields using specific terms for loading and injury risk during ground contact had low a low percentage of agreement. Within ground contact fields, the participants did not appear to have difficulty identifying whether ground contact had occurred or not or, if so, in determining the nature of the object. The loading pattern description produced inconsistent results and agreement in fields assessing specific risk factors was lower than anticipated. To correct this, the specific factors were each addressed in their own field with simplified responses (yes/no/unsure). Region loaded was deleted as it could not be provided with a sufficient reference and inferences could be made from observation of risk factors and region struck during ground contact. Range of motion was changed from “was the affected joint placed in hyper-extension” to “did the observed motion exceed normal joint range of motion”.

As a result of the discussions, the consensus of the expert panel was used to make changes to the protocol to improve agreement. The changes were incorporated in a revised protocol which was tested in a second IRR study. The results of this study are presented in the following chapter.

155

156 CHAPTER SIX

TESTING THE REVISIONS TO THE PROTOCOL

The limited number of sports science studies that have tested the reliability of the analysis tool has been discussed earlier in this thesis in section 3.5.5. Fewer studies have tested the reliability of the qualitative analysis protocol then made changes to improve the reliability before testing the efficacy of those changes. The analysis protocol was developed according to the scientific criteria for qualitative research presented by Paton (2002) and fulfils the first four criteria. Following development of the tackle protocol in a repeatable systematic framework, the face and construct validity were confirmed by presenting the method to a panel of coaches. The first reliability study (IRR1) allowed for a number of ideas for analysing the tackle to be tested and developed by making modifications to improve rater agreement of the final protocol. The effects of the modifications that were made to improve the reliability of the analysis protocol were assessed in a second IRR study (IRR2).

6.1 Methods

IRR2 was completed during August 2007, 12 months after the conclusion of the IRR1. The substantial break between studies was applied to control for any learning effects that may occur through participation in the first inter-rater reliability study.

6.1.1 Participants and task

All four Australian based participants who assisted with IRR1 were contacted and invited to participate in IRR2. All participants accepted the invitation and no other individuals were recruited to the study. Because of the low completion rate amongst the UK participants they were not invited to participate. Each participant was provided with a detailed coding manual of the revised protocol. The updated coding

157 manual included a checklist of expectations for complete participation in the study and detailed procedural instructions for the use of analysis software (Appendix D, pages D-7 and D-41).

To test the reliability of the revised protocol, participants were asked to identify and code all tackles which met the tackle definition within two five minute passages of play. To avoid potential recall bias, neither of the two five minute passages of play videos that were used in IRR1 were used again. The two videos that were given to participants were from two colts (U21) games (Sydney grade rugby competition). The video was recorded by a professional camera operator as part of the rugby headgear study using a digital video camera. The video was digitised, clipped to the required length and saved to AVI format for use in IRR2. The videos were viewed using Snapper TM observational software (Webbsoft technologies.) which had been acquired following the first reliability study for a larger study of tackling technique (McIntosh, Savage, et al., 2010). The use of this system allowed for more accurate recording of tackle event reference time and for easier navigation through the video. All participants were directed to identify the events that met the tackle definition using snapper and to then complete both upper level and lower level coding in a database that had been written in MS Access TM.

6.1.2 Training

An updated tackle coding manual, reflecting the changes to improve agreement outlined in section 5.3, was developed and provided to all participants during a one hour training seminar that was held at UNSW. The purpose of the seminar was to provide instruction on the desired application of the protocol and outline the study expectations. During the seminar for the second reliability study, the tackle analysis protocol was presented independently to the first seminar, i.e. the protocol was presented in its entirety rather than simply highlighting the revisions to the protocol. The importance of accurately identifying the tackle event reference time and the dependence of the reference time on the type of tackle that the participant adjudicated were highlighted. All participants were asked to complete the required

158 task within two days of the seminar using one of two computers that were made available to them for the purpose.

6.2 Results

Of the participants that were recruited to the study, all four completed the minimum requirements and coded both five minute passages of play. The same expert rater who completed the codings for the first inter-rater reliability study also completed the IRR2 tasks. The ratings of the expert were included with the results of the other participants. Therefore, the ratings from five coders were used for the second reliability study. A comparison of agreement between IRR1 and IRR2 is presented in Figure 6.1. An overview of the mean agreement rates according to the analysis level or section is presented in Figure 6.2. The coefficient of determination (R2) for the linear regression of IRR1 and IRR2 was 0.37 indicating that there was not a strong correlation between the two studies.

1.20 Better agreement in IRR1 Good agreement in both studies

1.00

0.80

0.60

0.40 IRR1 agreement

0.20

Poor agreement in both studies Better agreement in IRR2 0.00 0.00 0.20 0.40 0.60 0.80 1.00 1.20 IRR2 agreement

Figure 6.1: Plot of agreement in IRR1 compared to IRR2. R2=0.369.

159 All tables presenting the results of reliability testing within this chapter also present the percentage change in the observed agreement rate between the first and second inter rater reliability studies.

6.2.1 Tackle definition

There were twenty eight tackle events which met the study’s definition of a tackle in the two five minute passages of play. The mean proportion of agreement between participants when identifying tackles was moderate (70%). The average measures ICC was 0.70 (95% CI: 0.53 to 0.82). The mean number of tackles that were identified by each participant was 30 (SD = 3.2). While none of the participants correctly identified all 28 tackles, one participant was able to correctly identify 27 tackles and another correctly identified 26 (Table 6.1). When ‘missed tackles’ were excluded from the comparison, the percentage of agreement increased to 80%.

Number of Total number tackles of tackles correctly Number of Participant identified identified (%) other events 1 26 21 (75) 5 2 33 27 (96) 6 3 32 23 (82) 9 4 33 26 (92) 7 expert 28 28 (100) 0 Mean (SD) 30.4 (3.2) 25 (2.9) 5.4 (3.4) Table 6.1: The number of tackles identified in IRR2 including tackles correctly identified according to the study definition and other events that were not tackles according to the study’s definition

6.2.2 The upper level

The results of the upper level analysis are presented in Table 6.2. The mean agreement rate for the twenty two fields in the upper level analysis was 0.75. The three fields with the highest agreement rates were fields evaluating ground and weather conditions and the field identifying whether the Ball-carrier was tackled while in the process of scoring a try. The fields where the lowest agreement rates

160 were observed were the determination of the tackle type and the fields assessing the relative height and body mass of the Ball-carrier with respect to the Tackler. All other fields in the upper level had agreement rates above 0.50 and nine fields had agreement above 0.80. There were obvious improvements in the observed agreement for four fields (Ball-carrier and Tackler team identification, ground conditions and not a tackle). There were decreases in agreement when evaluating the number of Tacklers and the phase of play.

Tackle analysis protocol Number of fields: 98 Mean agreement rate: 0.71

Upper level Lower level analysis Generic Description of the tackle Detailed analysis of the tackle Number of fields: 22 and ground contact for the ball Mean agreement rate: 0.75 carrier and Tackler Number of fields: 76 Mean agreement rate: 0.69

Ball carrier tackle Tackler tackle contact contact analysis analysis Number of fields: 20 Number of fields: 20 Mean agreement rate: 0.67 Mean agreement rate: 0.63

Ball carrier ground Tackler ground contact contact analysis analysis Number of fields: 18 Number of fields: 18 Mean agreement rate: 0.69 Mean agreement rate: 0.79

Figure 6.2: An overview of the number of fields in the analysis and the mean agreement rate for the analysis levels

161 Upper level analysis fields Field Name Agreement % change Event type 0.82 90.8% Ball-carrier position 0.58 - Ball-carriers team 0.95 179.7% Tackling players team 0.96 185.9% Tackle type 0.43* 91.8% Number of Tacklers 0.63 71.8% Tackle sequence 0.64 83.4% Tackle complete 0.80 98.3% Not a tackle 0.69 154.1% Coded further 0.82 101.3% Phase before 0.58 118.6% Phase after 0.53 78.8% Retains ball 0.82 100.2% Field half 0.69 94.3% Field aisle 0.72 109.3% Field corridor 0.81 117.3% Impact force 0.62 97.7% Ground dry 1.00 137.8% Raining 1.00 105.3% Attempting to score 1.00 104.1% Relative height ID 0.43 89.6% Relative mass ID 0.45 93.0% Table 6.2: Agreement rates in Upper level fields for IRR2 and percent change (IRR2/IRR1) *Agreement rates changed when similar variables were grouped

The agreement for important event identifiers, Event type, tackle complete and further coding were above 0.80 and similar to the agreement rates reported in the first study. The agreement for the number of Tacklers (0.62) and the sequence of Tackler engagement (0.64) were lower than the observed agreement rates for the first inter rater study (72% and 83% respectively). Within the sequence field the agreement rate for one-on-one tackles was 0.72, sequential 0.47 and simultaneous 0.60. When multiple tackle sequences (simultaneous and sequential) were grouped the observed agreement rate increased to 0.68.

The analysis fields evaluating the position of the tackle on the field produced agreement rates between 0.59 and 0.81, which were similar to the results of the

162 first IRR study. There was variation in the results for the phase of play before and after between the two studies. Phase of play before increased, while phase of play after decreased. Inspection of the raw data indicated that some circumstances that were described by participants as tackles were described by others as rucks, while there was also apparent difficulty when discerning kicks in general play from kick off restarts. Open play or backline move, which had an agreement rate of 0.7 for both fields in IRR1 decreased to 0.13 in IRR2.

6.2.3 The lower level

6.2.3.1 The Ball-carrier: assessment of contact characteristics

The tackle contact analysis fields for the Ball-carrier are presented in Table 6.3. The mean agreement rate for the Ball-carrier tackle contact was 0.67. The three fields with the highest agreement rate were the awareness of the Tackler, the orientation of the Ball-carrier to the direction of travel, and evaluating whether the Ball-carrier was lifted during the tackle. The field with the lowest agreement rate evaluated the position of the spine/upper body during the tackle impact (back straight; 0.47). The greatest improvements between IRR1 and IRR2 were the fields evaluating the Ball-carriers body height immediately prior to the tackle impact, evaluating the direction of travel of the Ball-carrier after the tackle and describing knee flexion/extension. The fields were negative changes were observed were the fields evaluating the flexion of the spine and head and neck position. All other fields showed either moderate increases of between 5 and 10% or minor deviations from agreement observed during IRR1.

163 Agreement in Ball-carrier analysis fields for the tackle contact Field name Agreement % change Position ID 0.71 107.7% Evasion ID 0.61 100.9% Aware of Tackler 0.85 103.5% Team mates in support 0.75 103.1% Speed 0.67 118.8% Direction of travel 0.64 108.2% Ball carry method 0.63 114.4% Orientation to direction of travel 0.82 107.6% Back straight 0.47 75.0% Shoulders rounded 0.50 97.3% Steps 0.75 119.3% Knees straight 0.73 131.9% Tackle direction 0.71 102.5% Lifted in tackle 1.00 110.7% Region struck 0.67 149.6% Head and neck position 0.62 91.0% Height 0.70 171.2% Small steps in contact 0.61 108.7% Direction after tackle 0.51 159.3% Tackle bust method 0.48 114.1% Table 6.3: Agreement rates in fields evaluating the tackle impact for the Ball- carrier *Agreement rates changed when similar variables were grouped

The agreement rates amongst participants for fields evaluating body posture were mixed. The fields evaluating shoulder protraction and extension of the spine were below the average agreement for this component of the analysis (0.50 and 0.47 respectively). However, the fields evaluating the Ball-carriers body height or posture and the knee flexion/extension were both above 0.70 (0.73 and 0.75 respectively). The field evaluating the body region struck during the tackle impact was again poor (0.38) but the observed agreement rate increased to 0.67 when adjacent body regions were pooled (as for the IRR1).

The observed agreement rates for fields using rugby specific terminology were varied and the agreement rates between IRR1 and IRR2 were similar. The field evaluating the support of team mates received the highest agreement (0.75) while the field describing the tackle bust method produced the lowest agreement rate

164 (0.48). The evasion technique that was employed by the Ball-carrier and the ball carry method resulted in similar agreement rates.

Of the fields describing speed and direction of the tackle event there was an improvement in agreement of almost 60% from IRR1 to IRR2 when evaluating the displacement of the Ball-carrier after the tackle according to a cardinal system, although the observed agreement rate of 0.51 was lower than the rate for most other fields in the protocol. The other directional field for the Ball-carrier at tackle impact, direction of travel, resulted in a higher agreement rate (0.64) but the change between the reliability studies was not as great. The direction of tackle origin produced an agreement rate of 0.70 while the evaluation of the player speed resulted in an agreement rate of 0.67.

6.2.3.2 The Tackler: assessment of contact characteristics

The results for the tackle contact analysis for the Tackler are presented in Table 6.4. The mean agreement rate for the twenty fields evaluating the tackle contact for the Tackler was 0.63. The three fields with the highest rate of agreement assessed the orientation to the direction of travel (0.80), the Tackler’s position or jersey number (0.80) and if the Tackler had a lower body position than the Ball-carrier (0.79). The agreement rates in these fields were similar to results of IRR1. The field with the lowest agreement rate evaluated the Tackler’s direction of travel or displacement after the tackle (0.36). The greatest improvements between IRR1 and IRR2 were the fields evaluating the Tackler’s body height immediately prior to the tackle impact, evaluating the direction of travel of the Tackler before tackle and describing the development of power in the tackle through extension of the lower body. The fields were negative changes were observed were the fields evaluating the tracking of the Ball-carrier and identifying if there was a secondary collision with another Tackler during the tackle. All other fields showed either moderate increases of between 5 and 10% or only minor deviations of less than 5% from the agreement observed during IRR1.

165 Agreement in Tackler analysis fields for the tackle contact Field name Agreement % change Tackler position ID 0.80 116.6% Eyes on Ball-carrier 0.61 66.5% Speed 0.59 124.5% Direction of travel 0.44 183.5% Orientation to direction of travel 0.80 112.1% Back straight 0.59 93.4% Lower body position than Ball-carrier 0.79 111.8% Feet alignment 0.69 100.8% Stance width 0.44 112.0% Steps 0.54 88.1% Knees straight 0.73 118.1% Feet preparation 0.55 141.7% Extends lower body 0.64 148.6% Arms grapple Ball-carrier 0.69 92.8% Head in tackle 0.50 109.3% Body region struck 0.67 87.0% Head and neck position 0.60 109.6% Height 0.74 186.0% Direction after tackle 0.36 129.9% Secondary impact 0.56 65.9% Table 6.4: Percentage of agreement in fields evaluating tackle contact for the Tackler *Agreement rates changed when similar variables were grouped

The agreement rate in fields evaluating the Tackler’s body position was mixed. The fields evaluating stance width and extension of the neck and spine were below the average agreement for this component of the analysis (0.44, 0.60 and 0.59 respectively). However, the fields evaluating the Tackler’s body height or posture and the knee flexion/extension were both above 0.70 (0.74 and 0.73 respectively). Both of these trends support the findings for the Ball-carrier in corresponding fields. The field evaluating the body region struck during the tackle impact was again poor (0.45) but once again the observed agreement rate increased to 0.67 when adjacent body regions were pooled.

The agreement rate observed in the three fields evaluating skills using rugby specific terms varied. The field evaluating use of the arms to grapple the Ball- carrier received the highest agreement (0.69) while the field describing the head

166 position produced the lowest agreement rate (0.50). The Tackler’s feet preparation produced an agreement rate of 0.55, an improvement on IRR1 of 42%. There were only moderate changes of less than 10% between the studies in the other two fields.

Of the fields evaluating the physical principles of the Tackler before and during the tackle event there was an improvement in agreement of almost 80% from IRR1 to IRR2 when evaluating the direction of travel for the Tackler, although the observed agreement of 0.44 was the second lowest agreement rate for Tackler tackle contact. The lowest agreement occurred in the other directional field for the Tackler at tackle impact, Tackler’s displacement after the tackle (0.36). The evaluation of the player speed resulted in an agreement of 50.9.

6.2.4 Ground contact

6.2.4.1 The Ball-carrier: assessment of ground contact characteristics

The results of fields evaluating ground contact for the Ball-carrier are presented in Table 6.5. The mean agreement rate between all participants was 0.69. The fields identifying that ground contact occurred and describing the striking object for the Ball-carrier had the highest rates of agreement for the Ball-carrier at ground contact in both reliability studies. The body contact fields once again produced agreement rates below the mean agreement for this level of the analysis and the agreement rates for the nominated second and third body regions struck were 0.30 or below. However, there was a slight improvement in agreement when identifying the first body region struck during ground contact from 0.31 to 0.49 (158%). Agreement for the final position of the Ball-carrier following the tackle and secondary impact was 0.71, 36% more than the corresponding field in IRR1, and evaluation of injury to the Ball-carrier improved from 0.51 in the first inter-rater reliability study to produce perfect agreement in IRR2. The observed agreement rate for the falling posture of the Ball-carrier was 0.49.

167 Agreement in Ball-carrier analysis fields for secondary/ground contact Field Name Agreement % change Did ground contact occur? 0.86 114.3% Striking object 0.96 96.0% First body region struck 0.49 158.2% Second body region struck* 0.25 - Third body region struck* 0.30 - Final position of the Ball-carrier after ground contact 0.71 136.0% Injury associated with ground contact 1.00 184.9% Axial loading during ground contact* 0.77 - Head or neck impact observed? * 0.84 - Fall to thorax or shoulder* 0.61 - Falls to back or buttocks* 0.80 - Lower limb locked upper body twisting* 0.88 - Limb injured free movement prevented 0.72 163.0% Lifted and turned* 1.00 - Motion exceeds normal ROM 1.00 167.6% Tackler contributes to load 0.49 83.7% Crushed after tackle or during ground contact* 0.48 - Falling position after tackle 0.49 88.1% Table 6.5: Agreement rates in fields evaluating Ball-carrier ground contact * new analysis field for IRR2

Improvements were observed in the agreement rates for the fields assessing loading patterns and specific risk factors following changes to protocol. The fields assessing impact to the head and neck, a fall to the back or buttocks, and forced rotation of a body segment in opposition to another produced agreement rates 0.80 and above. Agreement rates above 0.70 were observed in all other fields assessing specific risk factors apart from the field evaluating impact to the shoulder or thorax where an agreement rate of 0.61 was produced.

6.2.4.2 The Tackler: assessment of ground contact characteristics

The results of fields evaluating ground contact for the Tackler are presented in Table 6.6. The mean agreement rate between the five participants in all fields was 0.79. The highest agreement was observed in the altered fields assessing specific risk factors. However, the results of these fields should be interpreted with caution because in several of the fields where a perfect agreement (1.00 or 100%) was

168 achieved, the targeted factor was not observed in a tackle by any participant. The fields identifying that ground contact occurred and describing the nature of the striking object had agreement rates above 0.85 and support the consistently high agreement rates in these fields for both the Ball-carrier and Tackler. The field with the lowest rate of agreement among participants was the evaluation of the body region struck. Unlike the Ball-carrier, the lowest agreement in IRR2 for the Tackler was recorded for the nomination of the first body region struck (0.38); the third body region produced a higher agreement rate (0.68).

Agreement in Tackler analysis fields for secondary/ground contact Field name Agreement % change Was there a ground/secondary contact 0.85 72.3% What was the striking object 0.87 89.3% First body region struck 0.38 30.2% Second body region struck* 0.44 - Third body region struck* 0.68 - Final position of the Tackler after ground contact 0.60 50.6% Injury associated with ground contact 1.00 68.3% Axial loading to Tackler* 0.85 - Head or neck impact to Tackler* 1.00 - Fall to thorax or shoulder* 0.73 - Falls to back or buttocks* 0.78 - Lower limb locked upper body twisting* 1.00 - Limb injured free movement prevented 0.95 136.8% Lifted and turned* 1.00 - Motion exceeds normal ROM 1.00 160.2% Ball-carrier contributes to load* 0.83 - Tackler crushed* 0.85 - Tackler falling position 0.55 48.0% Table 6.6: Agreement rates in fields evaluating ground contact for the Tackler * new analysis field for IRR2

The fields evaluating the loading and specific factors demonstrated higher agreement than the corresponding fields testing in the first reliability study. Agreement rates in eight of the ten fields were above 0.80. When compared to the Ball-carrier, better agreement was observed in the fields assessing crush loading and another player’s contribution to load experienced by the Tackler. The fall to the shoulder or thorax also had higher agreement amongst the participants for the

169 Tackler compared to the Ball-carrier. Finally, evaluation of the falling posture and final position of the Tackler after the tackle resulted in agreement rates of 0.55 and 0.60 respectively. These results were similar to the agreement rates that were observed during the first reliability study and are comparable to agreement for corresponding fields for the Ball-carrier in IRR2.

6.3 Summary and Discussion

Few studies have evaluated reliability of a qualitative technique analysis method following changes to improve agreement. There was an improvement in the mean agreement rate of the protocol in IRR2 following changes that were made during the meeting with the expert panel. The number of fields with substantial agreement (>70% or 0.7) doubled to 48. Agreement in tackle type, the field on which the tackle event reference time was based, which produced fair agreement in IRR1 did not improve in IRR2. This has significant implications for how an analysis with the protocol should be delivered to improve reliability and confidence in the results. Agreement for evaluations direction improved in all cases but remained fair to moderate and body regions were also observed to produce moderate agreement when similar regions were grouped.

While one participant group was constant between the two studies, the second group from the UK was unable to participate in the second IRR study. Therefore, improvements in agreement must be interpreted with some caution. For example, there was a significant improvement in agreement for identification of player team between the studies, even though a detailed description of all teams in the video were included in the IRR1 coder manual (appendix A). While identification of player team may be inconsequential compared to other fields such as tackle type and body region struck, it is possible that agreement in these fields was also influenced by the absence of the second group of participants from the UK. This could be assessed by comparing agreement between Australian based participants in the first and second studies.

170 With these considerations in mind, the improvement in agreement was promising and with additional participant instruction, ongoing monitoring of agreement and coding quality and careful management of the weaknesses of the method that have been identified (e.g. tackle type and body region), the protocol presents potential as a tool to describe the tackle event. The following chapter will present a sample analysis with the tackle protocol to demonstrate its application and how internal consistency of codings can be used to identify results that require clarification.

171

172 CHAPTER SEVEN

APPLICATION OF THE PROTOCOL TO A SAMPLE OF

TACKLES

Previous chapters have described the development and reliability testing of the tackle analysis protocol. This chapter will present the reader with an example of the utility of the protocol by providing results from its application to a sample of tackles. The tackle analysis that is presented in this chapter has been performed on tackles extracted from a project led by Associate Professor McIntosh. The Master’s candidate acted as project officer and was responsible for the day to day supervision of a team of five research assistants that assisted with the coding on the project.

The methods that were used in the larger study have been described elsewhere (McIntosh, Savage, et al., 2010). The Master’s candidate contributed to the development of the method that was used in the larger study in consultation with the projects investigators, taking into account the limitations of the protocol that had been identified during reliability testing. In summary, video of 340 games was collected from four levels of play and 25 games from each level of play were randomly selected (100 videos in total). Tackles were screened and coded at the upper level by the master’s candidate while the lower level coding was completed by a team of research assistants. Coding of one tackle completely at the upper and lower level was intensive and to code one half fully took approximately four hours at the upper level and sixteen hours at the lower level (twenty hours in total). Upper level coding was completed in Snapper (Webbsoft technologies) and the codings were then exported for lower level analysis using Microsoft Access TM. The Master’s candidate designed and programmed the database and the graphical user interface used for lower level analyses is presented in Appendix E.

173 7.1 Methods

Tackles were randomly selected from 6,618 tackles that were analysed in a larger study of tackle technique and injury risk (McIntosh, Savage, et al., 2010). To select the tackles for the analysis, the full dataset was ordered by the field ‘level of play’ (see Appendix D, IRR2 coder manual, page 11-D) in SPSS® (IBM Corporation) and the first one hundred tackles were copied to a new dataset for further analysis. The application of the protocol was assessed by evaluating completeness, internal consistency, and the description of the tackle skill with reference to coaching technique and injury risk factors. The latter is intended to provide examples of the insights that might be gained from using the tackle analysis protocol in a well designed study. Descriptive statistics were calculated from cross tabulations produced in SPSS version 18. The full dataset had previously undergone one consistency check to remove obvious errors as part of the larger study (McIntosh, Savage, et al., 2010).

To describe the completeness of the data, the number of blank values and ‘unsure’ codings in each field were enumerated. A proportion of completion was calculated by dividing the observed frequency of complete values in a field by the number of codings available for analysis with the field. The proportion of completion of each field was then used to calculate the mean proportion of completion for all fields in the protocol. An additional measure of completeness, the completion rate, the number of tackles that could be completely coded correctly according to the protocol definitions document, was also calculated and is presented per 100 codings. Triangulation of fields that were related or had a similar purpose in the analysis protocol was performed to assess internal consistency and accuracy of the analysis.

To present the reader with an example of the utility of the tackle analysis protocol, the conformity of tackling skills observed in the sample of tackles with coaching guidelines at the time that the protocol was developed (ARU, 2006a; NZRU & ACC, 2005a) and the presence of injury risk factors were evaluated. Fields assessing the critical features for safely and effectively tackling and receiving a

174 tackle (section 4.2.3.2 and Table 4.1) were evaluated according to tackle type and other selected fields such as impact force, position grouping and relative player size. A number of the risk factors for injury that were identified in section 4.2.3.4 were assessed.

7.2 Results

Of the 100 tackles analysed, 73 were identified as ‘general tackles’ that could be coded completely at the upper and lower level and 27, where poor video quality or obstruction of the event permitted coding only at the upper level, were identified as ‘obscured’. There were no medical events (knockdown, medical aid sought, player leaving the field) in the sample of tackles.

7.2.1 Completion and overview of the sample

The proportion of completion for the sample in all fields of the tackle analysis protocol is presented in appendix F and a summary is presented in Table 7.1. The mean proportion of completion in all fields of the tackle analysis protocol was 96%, i.e. for each tackle that was coded at the lower level, a value was entered correctly in a field, including coding as ‘unsure’, on 96 occasions out of 100. In contrast, the rate of completion was 72/100. Reviewing completion by the level of analysis, all fields in the upper level had a valid entry for all tackles (100%) while completion in the lower level was considerably less, only 6 of the 65 fields (12%) in the lower level assessment of contact characteristics were complete for all tackles. Three of the lower level fields that were complete for this analysis identified the jersey number of the player involved (Ball-carrier, Tackler and second Tackler) and a further three fields confirmed ground contact for the Ball- carrier or Tackler/s. An additional three lower level fields of additional notes and database generated content for record identification and linking were not included in this analysis.

175 Eleven fields were incomplete for more than 10% of tackles. These fields were mostly related to evaluating aspects of posture and body position and size. The field evaluating the Ball-carriers awareness of the Tackler was the least complete (36%), followed by Ball-carrier support and Ball-carrier steps into contact (both 27%). The fields evaluating the relative height and mass of the Ball-carrier with respect to the Tackler were incomplete in 11 of 73 cases (15%). Other fields assessing posture of the Ball-carrier (back straight, shoulders rounded, knees straight) and Tackler (back straight), and the third region struck during ground contact for both the Ball- carrier and Tackler were amongst those with a large proportion of incomplete codings.

Correctly No. No. Proportion Analysis level complete fields codings complete fields (%) Upper level 28 100 100 100 Lower level Tackle impact Miscellaneous 6 73 50 95.2 Ball-carrier 19 73 5 87.1 Tackler 20 73 5 88.3 2nd Tackler 20 15 5 85.4 Ground contact Ball-carrier 17 48 67 97.3 Tackler 17 42 71 98.3 2nd Tackler 17 5 100 100 Total 144 100 51 94 Table 7.1: Number of fields and completion rate for the tackles analysed.

There were 15 ‘simultaneous’ tackles in the sample (where two Tacklers tackled the Ball-carrier at the same time). Fields in the codings for two of these tackles were generally incomplete; however, the proportion of completion (85.4%) was similar to proportion recorded for the Ball-carrier and Tackler (87.1% and 88.3% respectively).

Ground contact was made by at least one of the players involved in the tackle in 58 of the 100 tackles. The Ball-carrier went to ground slightly more often than the

176 Tackler (48% & 42% respectively) and both players went to ground in 32 of these 58 tackles. The completion for ground contact fields was better than lower level tackle impact analysis and a higher proportion of fields were completed correctly for all tackles and a lower number of mean records incomplete.

In addition to completeness of the coding in each field, a number of ‘unsure’ responses were observed in the analysis results of this sample of tackles. Of the 144 user completed fields in the protocol, 40 had been coded ‘unsure’ or ‘unknown’ at least once (Table 7.2). The fields with the highest proportion of unsure events were the body region struck during ground contact, particularly fields requiring identification of second and third regions. Nine of the fields were assessed with a simplified (yes/no/unsure) response. Of these 9 fields, the highest proportion of ‘unsure’ values was seen in the field evaluating whether the Tackler grappled the Ball-carrier with their arms (13% of codings with the field). Other fields using this response pattern had a low proportion of ‘unsure’ codings (between 1 and 6%).

7.2.2 Internal consistency of similar protocol fields

Good internal consistency was demonstrated when triangulating similar fields in the main event descriptors. In the sample of tackles analysed, all tackles that were not coded at the lower level were correctly identified as ‘obscured’. The field describing what was observed when the tackle did not go to ground was correctly coded and completed only for tackles that did not meet IRB Law 15 (“going to ground”, see page 2) and as “not an IRB tackle” for all other tackles (Table 7.3). Comparing fields assessing the impact sequence and the number of Tacklers, all one on one tackles were correctly coded involving only one Tackler, and simultaneous and sequential tackles were correctly coded involving multiple Tacklers. All tackles that had been coded to describe ground contact characteristics had correctly identified that ground contact occurred to the player corresponding with the analysis at the lower level tackle impact descriptors.

177 Proportion Analysis level Field name ‘unsure’ (%) Upper level Phase of play before 1.0 Phase of play after 1.0 Lower level Relative height of Ball-carrier and Tackler 8.2 Relative mass of Ball-carrier and Tackler 5.5 Ball-carrier tackle Team mates in support* 1.4 contact Ball carry method 2.7 Shoulders rounded* 2.7 Steps into tackle* 1.4 Knees straight* 4.1 Body region struck 21.9 Tackle bust method 5.5 Tackler(s) tackle Direction of travel 5.5 contact Orientation to direction of travel 1.4 Back straight* 2.7 Feet alignment 2.7 Stance width 5.5 Steps into tackle* 5.5 Speed 9.6 Knees straight* 2.7 Feet preparation 5.5 Arms grapple* 4.1 Head in tackle 1.4 Body region struck 16.4 Head and neck position 4.1 Second Tackler arms grapple* 13.3 Second Tackler body region struck 26.7 Ground contact Ball-carrier Region Struck 1 20.8 Ball-carrier Region Struck 2 33.3 Ball-carrier Region Struck 3 50.0 Ball-carrier falling position 10.4 BC falling posture 6.3 Tackler Region Struck 1 31.0 Tackler Region Struck 2 38.1 Tackler Region Struck 3 57.1 Tackler falling position 14.3 Tackler falling posture 2.4 Tackler 2 Region Struck 1 80.0 Tackler 2 Region Struck 2 100.0 Tackler 2 Region Struck 3 100.0 Tackler 2 falling position 20.0 Tackler 2 falling posture 20.0 Table 7.2: Fields with ‘unsure’ or ‘unknown’ *field assessed on simplified scale (yes/no/unsure)

178 Two Ball-carrier identification fields were included in the protocol, one at the lower level and one at the upper level. The proportion of agreement between the two coders for these fields was 60%. However, in a further 35% of cases, a playing position was identified by a coder at the upper while the corresponding coder at the lower level evaluated the playing position as obscured. There was clear disagreement in only 5% of the cases.

Field: Field: Tackle complete If not a tackle what occurred? Yes No Unsure Tackle complete (IRB Tackle) 71 0 0 Missed Tackle 010 Break Tackle 0180 Held Up/Maul 020 Offload from feet 080 Unsure 000

Table 7.3: Cross tabulation of the raw count for tackle complete against what happened if the tackle was not complete demonstrating the internal consistency between the fields

A comparison between the tackle complete field and ground contact (and the ground contact record) presented a discrepancy between analysis fields. A negative coding for tackle complete indicates that the tackle did not go to ground and that ground contact should have been completed. However, in at least 6 tackles the ground contact record had been completed for a Ball-carrier who had “offloaded from feet” (Table 7.4). Similarly there were 11 tackles where no ground contact had been recorded but where the tackle was identified as complete. The total number of these cases is small (17%) but approaching one fifth of the sample of tackles.

Discrepancies were also observed between the tackle type that was employed and the observed body region struck. Only 43% of tackles were coded correctly so that the tackle type corresponded with a particular body region. The best results were observed for the jersey (5 of 5 tackles) and arm tackles (6 of 7 tackles) while the active shoulder tackle, the second most frequent tackle type, was correctly linked with the shoulder or upper arm in 12 of 18 tackles. The smother tackle, the most

179 frequently observed tackle, was correctly linked with the chest in only 12% of cases (4 of 32 tackles) while the ankle tap (1 case) and passive shoulder tackle (3 cases) were not correctly linked with body region. Similarly, triangulating the directional fields provided another example of the utility of cross referencing fields in the protocol to ensure continuity and validity of the data. While two of the twenty six tackles that originated from in front of the Ball-carrier struck were identified as making contact with the Ball-carriers back. After highlighting these cases they could be reviewed to ensure the accuracy of the coding.

Field: Ball-carrier ground contact

Field: If not a tackle what Not coded occurred? Yes No at lower level

Tackle Complete (IRB Tackle) 41 11 19 Missed Tackle 010 Break Tackle 0126 Held Up/Maul 011 Offload from feet 611 Unsure 000

Table 7.4: Cross tabulation of the raw count for tackle complete against ground contact coding demonstrating the internal validity between the fields.

7.2.3 Player size, tackle technique and impact force

The most common tackle type that was observed in the sample was the smother tackle (45 of 100 tackles), followed by the active shoulder tackle (31 of 100 tackles) and the arm tackle (11 of 100 tackles). In the sample of 100 tackles, the backs position grouping was involved as the Tackler more often than forwards (45% and 26% respectively), although for a large proportion of tackles the position of the Tackler could not be determined (Table 7.5). Tackles were most often executed by backs on backs (19% of 73 tackles). The outside centre (eight tackles) was most often the Tackler and the left wing (twelve tackles) was most often the

180 Ball-carrier. A similar proportion of tackles by tackle type were observed for each position grouping (Table 7.6). Not enough tackles were included in the sample to make inferences regarding playing position and tackle type, but smother tackles were most commonly used by the No. 8 and Scrumhalf following a ruck or a tackle and the active shoulder tackle was most commonly used by the Outside centre following a backline move or tackle. For all tackle types, the most common phase of play after the tackles analysed was a ruck; and a backline move (26%) or another tackle (23%) were the most common phases of play before.

Ball- Tackler position grouping carrier Total (n) position Forward Back Reserve Obscured grouping Forward 9.6 11.0 0.0 6.8 20 Back 12.3 19.2 4.1 6.8 31 Reserve 0.0 1.4 0.0 4.1 4 Obscured 4.1 13.7 0.0 6.8 18 Total (n) 19 33 3 18 73 Table 7.5: Player grouping of the Ball-carrier and Tackler as a proportion of all tackles

Comparing tackle type by the subjectively assessed impact force (Table 7.7) indicates that active shoulder tackles were more likely to be assessed as high impact than smother tackles. The observation that the passive shoulder, jersey and ankle tap tackles were of low impact force also serves as a form of triangulation for the field and provides further evidence of internal validity. The main body regions struck for the Ball-carrier were the shoulder (19.2%), the back (13.7%) and the upper limb (12.3) while for the Tackler the regions struck were the forearm (37%), the shoulder (19.2%). A number of tackles (12.3%) were assessed to contact the upper body though the precise region could not be determined.

181 Tackler UL Tackle type position Shoulder Smother Other Total (n) grouping Active Forwards 26.3 52.6 21.1 19 Backs 33.3 48.5 18.2 33 Reserve 66.7 33.3 0.0 3 Obscured 11.1 44.4 44.4 18 Total (n) 20 35 18 73 Table 7.6: Tackle type as a proportion of player position grouping (rows add to 100%)

Impact Force Total Tackle type (n) High Low Unsure Active Shoulder 12 19 0 31 Passive Shoulder 0404 Jersey 0606 Ankle Tap 0303 Smother 342045 Arm Short/Long 110011 Total (n) 16 84 0 100 Table 7.7: Number of tackles by subjectively assessed impact force and tackle type

The relative height and mass of the Ball-carrier to the Tackler is presented in Table 7.8. The results show that for almost 23% of the tackles coded at the lower level, both the Ball-carrier and the Tackler were evaluated as of similar size, while for 21% the Ball-carrier was subjectively assessed to be both taller and heavier. When relative size of the players was considered as a proportion of the tackle type employed, the active shoulder tackle was observed most frequently when the Ball- carrier was taller (46%) and lighter (39%) than the Tackler. The smother tackle was observed most frequently when the Ball-carrier was of similar height (41%) and weight (48%) as the Tackler. There were insufficient numbers of other tackle types to assess the relationship between the relative size of the players and tackle type employed, however, when the other tackle types were grouped, similar trends were observed as for the active shoulder tackle, with the other tackle types likely to

182 be used where the Ball-carrier was taller (40%) and lighter (47%) than the Tackler. There were no clear trends in the subjectively assessed impact force of the tackle according to the relative size of the players owing to the small number of high impact tackles that were recorded in the sample analysed.

Relative height of Ball-carrier to the Tackler Relative mass of the Total Ball-carrier to the Larger Smaller Similar (n) Tackler than than Unsure size Tackler Tackler

Larger than Tackler 21.0 3.2 3.2 0 17

Smaller than Tackler 11.3 17.7 4.8 3.2 23

Similar size 3.2 3.2 22.6 0.0 18

Unsure 0 0 0 6.5 4

Total (n) 22 15 19 6 62

Table 7.8: Relative height by relative mass of the Ball-carrier to the Tackler as a proportion of all tackles.

7.2.4 Tackler compliance with promoted tackling technique

The results of the analysis for the Tackler show that there is some discrepancy between the advocated tackling technique and actual execution of the skill. The Tackler did not grapple the Ball-carrier with their arms in the majority of tackles coded at the lower level (59%). Even when making an active shoulder tackle, the advocated tackling style, the Tackler grappled with their arms in only forty percent of tackles and when using a smother technique arm grapple was observed in only twenty percent of cases. The Tacklers head position was observed to be beside or behind the Ball-carrier as advocated in the coaching literature in 55 percent of tackles and above or in front of the Ball-carrier in thirty three percent of tackles. Of potential concern in this sample of tackles was head position using the passive shoulder tackle, where in two out of three tackles (67%) the Tacklers were

183 determined to have their head in a potentially injurious position in front or above the Tackler. The Tackler was observed to have their head up (cervical spine extended) in the majority of tackles analysed (74%), however, of the technique types, the active shoulder tackle had the highest observed frequency of Tacklers with their neck flexed (chin on their chest, 7 of 20 cases). Leg drive appears to be under utilised in this sample of tackles, the Tackler extended the lower limb to exhibit leg drive into the tackle in only five percent of cases. Tracking of the Ball- carrier (or Tackler awareness), an important skill when executing the tackle safely and effectively, was present in almost ninety percent of the tackles analysed. The Tackler fell to the ground separately from the Ball-carrier in the majority (35%) of tackles and fell on top of the Ball-carrier, as advocated in the coaching literature in only nine percent of tackles. However, the Tackler fell on top of the Ball-carrier most often in the passive shoulder tackle which, defined in the coding manual as latching onto the Ball-carrier using their arms and pulling them to the ground, indicates that this tackle may not have been coded correctly. Positioning of the back for the Tackler was poor for all observed tackle types.

7.2.5 Ball-carrier compliance with promoted tackling technique

The advocated attributes of technique were more common for the Ball-carrier, and four of seven attributes were performed correctly. The Ball-carrier was observed to have their shoulders rounded when entering contact in the majority of cases (51%) and was adjudged to be aware of the Tackler in 64% of cases. It should be noted that there were no tackles in this sample where the Ball-carrier was assessed as unaware of the Tackler, though the field did have a high rate of non-completion (36%), as previously discussed in section 7.2.1. Coinciding with awareness, the Ball-carrier had their head up in 68% of cases, and this proportion increased when being tackled using an active shoulder, presumably where they had a more upright stance. The Ball-carrier had the ball in two hands in 21% of cases and in the trailing arm the majority of tackles (45%). Of the fields that indicate poor compliance with the coaching guidelines, the Ball-carrier was observed to step into the tackle in only 10% of cases, did not take small steps in contact and was

184 observed to put out an arm to break their fall in almost one fifth of coded ground contact events.

7.2.6 Injury Risk factors

As has been previously identified in section 7.2.1, there were no injuries or medical events in this sample of tackles. The purpose of this analysis was to demonstrate the results that would be obtained through an analysis of fields evaluating the presence of injury risk factors identified in section 3.4.4.

It was not possible to present results for a number of risk factors. Level of play has not been used in this analysis because the tackles in this sample were extracted from one level of play. Foul play in the tackle according to the referee’s decision regarding the legality of tackles was not evaluated in the sample of tackles. However, the results for body region struck during the primary tackle contact indicate that the Ball-carriers head was struck in one of the seventy tackles (1.4%) for which the field was completed. The neck was not identified as a region struck for any of the tackles. Further, the number of tackles that a particular player was involved in was not assessed in this analysis of anonymous data. The application of Tackler engagement and tackle type has been previously discussed in section 7.2.3. Results concerning potential injury risk factors are summarised in the following paragraphs.

7.2.6.1 Direction of tackle origin

Thirty eight percent of tackles were observed to originate from in front of the Ball- carrier and sixteen percent from behind. Tackles from the left and right side of the Ball-carrier occurred in similar proportions (both 17%).

7.2.6.2 Awareness of the tackle

Tackler awareness was discussed in section 7.2.4. In 64% of tackles the Ball- carrier was adjudged aware of the Tackler. While the Ball-carrier was not evaluated as unaware of the Tackler in any of the tackles analysed, it should be stated that 36% of cases were not coded for this field. Comparing the field ‘tackle

185 direction’ with ‘awareness of the tackle’ did not support a hypothesis that non- coding of awareness field equated to an assessment that the Ball-carrier was unaware of the tackle. The proportion of tackles originating from in front and behind that were not coded for awareness was similar to the general prevalence of tackles from the front and back.

7.2.6.3 Player speed and stability

In the majority of cases the Ball-carrier was travelling fast prior to the tackle (81%). The Tackler was also travelling fast (55%) and in 40 tackles both the Ball- carrier and the Tackler were travelling at speed. In 3% of cases the Ball-carrier was travelling fast while the Tackler was still or stationary as the Ball-carrier approached. Only 6 of the 40 tackles where both players were moving quickly prior to the tackle were assessed subjectively as high impact. The remaining 36 were assessed to be low force. The main impact sequence observed when the Ball- carrier was moving quickly was the one on one tackle (59%) and the main tackle type was the smother (51%). The phase of play before the tackle did not affect the speed of the players involved in the tackle.

In 74% of tackles the Tackler was travelling ‘fast’ and had only one foot in contact with the ground. When still or stationary the Tackler was always observed to have their feet shoulder width apart or greater and in 3% of tackles the Tackler was on their knees when trying to execute the tackle. The Ball-carrier stability was evaluated by assessing whether the player stepped into the tackle and/or took small steps after being tackled. Based on these criteria, the Ball-carrier was observed to have poor stability. They did not step into the tackle (60%) or maintain small steps in contact (68%) in the majority of cases. However, in cases where small steps were taken in contact, the Ball-carrier was observed to break the tackle contact more often (26% compared to 14%). Other factors, including player size and velocity when entering the tackle may also play a role in this.

186 7.2.6.4 Field position

The frequency of tackles by field position is presented in Figure 7.1. The majority of tackles occurred in the oppositions half and in the mid-field aisle and corridor (37 of 100 tackles). The majority of tackles occurred in the midfield aisle (65%) with few tackles occurring in the left and right flanks (17 and 18% respectively). Few tackles in this sample were observed in either 22 metre zone and no tackles were observed in the in goal area.

Own half Oppositions half

In Mid- Mid- In Total goal 22 field field 22 goal (n)

Left flank 0 0 6 8 3 0 17

Mid-field 0 2 19 37 7 0 65

Right flank 0 0 10 7 1 0 18

Total (n) 0 2 35 52 11 0 100

Figure 7.1: Number of tackles by field position

7.2.6.5 Weather and pitch conditions

All of the tackles in this sample were taken from matches where it was not raining and the ground was dry. Table 7.9 presents an example investigating relationship between tackle type and these fields. Player speed and phase of play before and after are other potential analyses, to name a few, that could be conducted.

187 Ground Dry (n) Raining (n) Tackle type Yes No Yes No Shoulder Active 31 0 0 31 Shoulder passive 4 0 0 4 Jersey 6 0 0 6 Ankle Tap 3 0 0 3 Smother 45 0 0 45 Arm Short/Long 11 0 0 11 Obscured 0 0 0 0

Table 7.9: A presentation of tackle type by ground and weather conditions

7.3 Summary and discussion

This chapter has presented the application of the protocol to a sample of 100 tackles from elite level matches. The application of the coding method to this sample was largely complete for 96% of analysis fields. This indicates that the tackle analysis protocol can be applied as intended, at either the lower level or both upper and lower levels, on most occasions. Incomplete fields were generally restricted to the same tackle events, rather than randomly distributed across the 100 records. This may make it easier to identify, and address, errors in coding. The large proportion of incomplete fields in these tackles suggests that it may not have been possible to code them because of poor video quality or obstruction. The field variable ‘unsure’, while available in most fields was only used sparingly and accounted for less than 1.5% of total codings (230 ‘unsure’ values).

Ground contact was a common outcome for the tackle and occurred in 58% of the tackles in this sample. The Ball-carrier and Tackler went to ground in similar frequency. The most common tackle type was the smother tackle, a tackle which is not currently described in any coaching hand book, while tackles using the active shoulder method were assessed as being of high impact more frequently than other tackle types. The body region struck was generally poorly correlated with tackle type in spite of these two fields being linked in the definition provided in the

188 protocol coding manual. This aspect of the analysis protocol, which provides a method of assessing the internal consistency of these two important fields, requires closer scrutiny.

The consistency amongst similar fields in the protocol was generally good. Tackles that could not be coded at the lower level or for ground contact were correctly coded in other related fields. Tackles that were identified as not complete according to IRB Law 15 were correctly coded with what had occurred, however, a comparison between the tackle complete field and ground contact suggested that one of these fields may have been miscoded in some tackles. In at least six tackles the ground contact record had been completed where a Ball-carrier had been identified as ‘offloaded from feet’ in the ‘reason tackle incomplete’ field. It is possible that the Ball-carrier may still have made ground contact following the tackle, however, the tackle would not be complete under the law because the player was not in possession of the ball when they went to ground. Clearly, better instruction of coders in the use of this field is required.

The evaluation of some of the critical features of technique demonstrates another potential application of the protocol. The results for this sample of tackles suggest that the Tackler did not adhere to the advocated tackling technique, while for the Ball-carrier, four of the seven attributes were performed in the majority of observations.

This information that has been presented in this chapter could be used by the governing bodies of rugby union to monitor the take up of promoted tackling technique, evaluate the execution of specific skills and assess particular injury risks in targeted populations. Potentially the information collected could be used to meet desired outcomes of this research that were noted in the introduction. Several methods of assessing internal consistency of the protocol to highlight errors in analyses have also been demonstrated. Based on the assessment that was presented in this chapter, the protocol is capable of describing skill execution in the tackle and presents a useful tool for this purpose when the limitations that have been previously presented are carefully managed.

189

190 CHAPTER EIGHT

DISCUSSION

8.1 Selection of qualitative analysis and development of the protocol

The main aim of this research was to prepare a thorough analysis method for the tackle in rugby union that was capable of describing skill execution and injury risk. A qualitative analysis protocol was selected in preference to methods from quantitative and predictive frameworks because it presented a flexible method that was better suited to developing an understanding of the skill through the enumeration of selected parameters (Greenfield, et al., 2007; Kreighbaum & Barthels, 1996). Observation, one of the primary data collection techniques of qualitative analysis, is perhaps the oldest and most accessible tool for scientific investigation. It may be made in real time or from video without specialised equipment. Potentially, therefore, the same tool could be applied to address both research and coaching applications, albeit in a modified format.

The main criticism of qualitative analysis that was encountered during research into suitable analysis methods, and during the review of literature, was that it is prone to bias because of its subjective nature and was therefore unobjective and unreliable (Hamill & Knutzen, 1995). However, there is a counter argument that these weaknesses can be overcome through developing the qualitative analysis method ‘objectively’ (Patton, 1999). This may appear to be counterintuitive, and it is important to re-emphasise an observation from the introduction that, within qualitative analysis, objectivity does not refer to numerical measurement but to a reproducible description. Bartlett (2008) observed that a valid and reliable qualitative method is developed through rigorous experimental design. When this research commenced, there was no one framework or clear set of guidelines for the

191 development of a qualitative analysis method. The protocol of Wilson et al. (1999) and prior work of the research group of which the masters candidate was a member (McIntosh, Savage, et al., 2005) provided basic assessments of the tackle, but these were not of sufficient depth to provide the level of detail that was sought. Similarly, while a number of qualitative frameworks were identified, none presented a definitive ‘road map’ to reach the protocol ‘destination’ via a systematic and repeatable ‘highway’. The development process for the tackle analysis protocols presented in appendices A and D and described in Chapter Four aspired to present such a method.

The process of recording and describing the development of a qualitative analysis protocol was extremely complex and this may account as to why so few studies have attempted to record the development process of the protocols used in their research. The framework for developing the protocol was compiled from a number of sources including existing qualitative frameworks, identified in section 3.5.4, which largely nominated the identification of critical features as the primary component in the preparative phase (Arend & Higgins, 1976; Knudson & Morrison, 2002; McPherson, 1996). Knudson and Morrison (2002) also argue that the perspectives of different disciplines will differ when indentifying targets for evaluation. Consulting epidemiology and biomechanical perspectives was essential for this research because of the research questions. This research developed a protocol that was informed by theoretical models from these disciplines and an extensive review of literature (Chapter Three) to painstakingly identify and delineate which aspects should be included in the analysis. Aside from producing a larger number of fields than comparable technique analysis protocols, attempting to incorporate epidemiological and biomechanical parameters into the tackle analysis protocol produced a more flexible method that could be tailored to the specific needs of a project but also provide valuable biomechanical information for assessing skill execution and injury events.

Managing the information that was assembled and prioritising targets of analysis was also problematic. The volume of information that had been collected through

192 the literature review identified a large number of aspects in the tackle that could be observed. The assembled theoretical models and other frameworks were particularly useful in organising the features into an analysis with the intention of enhancing observer objectivity and reliability. During this phase (section 4.2.4) the scientific criteria for qualitative analysis proposed by Patton (2002) (Figure 3.4) were also identified from the literature and these became the benchmark for the arduous process of developing the tackle analysis protocol.

8.2 Validation

Justification for the inclusion of specific fields was presented in Chapter Four. The tackle analysis protocol underwent a number of informal phases of validation during its development. Initially, validation occurred in the form of developing face validity through consulting with the coaching literature to identify the critical features of technique, a common parameter of a number of qualitative research guidelines (Arend & Higgins, 1976). Once the protocol had been finalised it was presented to a panel of expert coaches who provided feedback on a number of the fields, as described in section 4.3. The discussion between the two research groups from UNSW and the RFU might also be considered an additional form of validation and the comparison of the two methods that had been developed revealed that they were remarkably similar. Finally, the protocol was presented to a panel of experts again following first IRR study where all fields were reviewed to determine if the analysis had been applied in the desired manner. The expert panel, in particular, has often been used to validate qualitative methods (David, et al., 2008) and provided a valuable opportunity for feedback, while developing the protocol in collaboration with a second party (the RFU team led by Dr. Kemp) also served to reinforce the validity of the protocol.

Future assessments of validation may examine some of the more subjective fields in the tackle protocol (such as specific loading factors, and force of impact etc.) by involving players from the games that were analysed and obtaining their feedback

193 on the ratings. The field describing event injury outcome was incorporated to assist in identifying events where an injury or medical event occurred. Considering the difficulties that have been experienced linking prospectively collected injury data with video (Andersen, Tenga, et al., 2004), this field would serve to highlight potentially high risk events which could then be passed to a panel of experts for further review and classification, similar to other studies (Andersen, Floerenes et al., 2004).

8.3 Reliability

The importance of reliability in qualitative analysis has been stated repeatedly and was one of the focuses of the questions that were identified in this research. Poor reliability may underestimate or fail to identify a risk factor or identify risks incorrectly based on bias (Dartt et al., 2009). The results of the literature search identified that only one other study has tested the reliability of a qualitative protocol following changes to improve agreement (David, et al., 2008).

Percentage of agreement was used as the primary measure of agreement for this study; as justification for changes to fields and assessment of improvements in agreement between IRR1 and IRR2. Percentage agreement was supported by Intraclass Correlation Coefficients, but only for the assessment of agreement between raters for tackles meeting the study definition. Several authors have argued that percentage of agreement is an unreliable measure because it overestimates agreement by not taking chance agreement into account (S. Burt & Punnett, 1999; Cohen, 1960). Percentage agreement continues to be widely used in spite of this criticism. There is also evidence that using a number of raters, and fields evaluating a target using three or more variables, decreases the occurrence of chance agreement (Uebersax, 1987). The large number of fields in this protocol excluded the use of Cohen’s Kappa to assess mean agreement between a number of the rater pairs. To use Fleiss Kappa more participants would have had to be included in the IRR studies and the burden of the task made this unrealistic.

194 Assessing agreement between all raters was considered sufficient to address the possibility of chance agreement, in addition to the consideration that most of the fields were assessed using three or more field variables.

The results of reliability testing have been discussed elsewhere, in sections 5.3 and 6.3. It cannot be stated with certainty that the tackle analysis protocol would be reliable in all situations. The mean agreement of the protocol in the second IRR study was 0.75, which may be considered substantial according to arbitrary scale of Landis and Koch (1977), modified for the purposes of this research (Table 5.1). Importantly, agreement for identifying a tackle event according to the study definition was generally high, despite the subjective nature of the definition.

There is evidence to suggest that the changes that were made to improve agreement were successful. The number of fields with agreement rates of 0.80 or above increased from 13 in IRR1 (16.6%) to 32 (40%) in IRR2. It was clear that the participants had some difficulty identifying the type of tackle and the sequence of multiple Tackler engagement. There were clear similarities between the results of the two IRR studies for fields where highest agreement was observed. Grouping variables in fields such as the tackle type body region struck resulted in an apparent improvement in agreement, but the loss of information must be weighed against the applicability of the analysis tool. An aspect of concern is agreement in the ‘tackle type’ field, previously discussed in section 7.3. How this may be overcome will be discussed in the next section.

8.4 Outcomes

While there was a general improvement in agreement between IRR1 and IRR2 following the changes that were made to improve reliability of the protocol, ‘tackle type’ was not as reliable as anticipated. The tackle event reference time (T0), a primary component of improving agreement in the protocol, was to be referenced to ‘tackle type’ and it was concerning that only fair agreement was observed for this field in the second IRR study. This may be due in part to the instruction used

195 in the IRR2 coder manual that tackle type should be assessed according to the body region struck (appendix D, page D-9), a field where agreement between raters was consistently low across both studies. However, it is possible that the effects of poor agreement may be minimised through utilising the structure of the protocol during project delivery. The structure of the protocol allows for the full analysis to be divided into two distinct components, the upper and lower level. This division was originally intended to allow the protocol to be applied in a more manageable fashion to tackle events. It is also possible that one experienced coder could be used to identify and code tackles at the upper level with a team of analysts providing support for lower level coding. This is how the protocol was operationalised in a recent study (McIntosh, Savage et al., 2010). Poor agreement in tackle type field may also be managed through a consensus approach, similar to other studies (Andersen, Floerenes, et al., 2004; Wilson, et al., 1999).

A field that is associated with the tackle type, body region struck, showed only fair agreement in both IRR studies, and while combining neighbouring body regions to improve agreement presents an alternative; this action needs to be carefully considered with respect to information that may be lost as a result. An additional consideration relates to discrepancies that were observed between the tackle type employed and the observed body region struck during the analysis of a sample of 100 tackles. Only 43% of tackles were coded correctly so that the tackle type corresponded with a particular body region. The best results were observed when contact was made with distinct, isolated body parts such as the arm. The smother tackle, the most frequently occurring tackle type that was observed was correctly linked with the chest in only 12% of cases. While it is possible that these results are correct, no cases of a smother tackle being executed with the head or neck or lower leg were observed, it also reinforces that evaluating body region reliably is difficult and seeking to confirm tackle type with body region struck needs monitoring during analysis, or review. At the very least, the definition of some tackle types, particularly the smother tackle, should be revisited to improve agreement. Current coaching material does not describe many of the other types of tackles that were included in the protocol, and this has the potential to contribute to

196 confusion when evaluating tackle type. It would, therefore, be useful to include the governing bodies of rugby union in this process.

Operationalising the protocol in the manner described, with an experienced person coding the upper level, may also address issues of agreement in other fields, such as sequence of tackler engagement (simultaneous vs. sequential tackles) and the phase of play before and after the tackle, where there was confusion when evaluating kicks (kick in general play vs. kick off/restart) and when a tackle became a ruck. In the absence of agreement above 0.70 (70%) in many of the fields of the lower level, any analysis using the protocol should analyse a large number of events.

The tackle analysis protocol has been used in two studies of tackling technique and injury risk (Fuller, et al., 2010; McIntosh, Savage, et al., 2010). The results of an analysis of a sample of 100 tackles (Chapter 7) provided an example of the results that might be obtained with the tackle analysis protocol. The results suggest that neither the Tackler nor the Ball-carrier adhere to many of the advocated skills in match situations at the elite level, where skills might be expected to be best. These results, if confirmed in a larger sample, might be used to inform changes in coaching technique and monitor their translation to match play. It was also interesting to observe that ground contact was made by the ball carrier in only 48% of the tackles examined. This observation demonstrates the effect that the tackle definition has on the number of events analysed. If the definition of a tackle under Law 15 was applied, then the number of ‘tackles’ analysed would decrease by half, resulting in a large number of tackles excluded from the description.

8.5 Strengths and weaknesses

Sofaer (1999) identifies one of the strengths of qualitative research as being its ability to deal with unforseen events. The large number of fields within the protocol described in this thesis is both a disadvantage for its application and an advantage in its flexibility. The number of fields resulted in an increased time

197 demand to apply the protocol to a target event. The burden of analysis with the protocol was addressed through its division into two parts, increasing the number of coders that can be used. The number of fields also increased the number of definitions that were required and meant that extreme care had to be used during the development phase to maximise potential user agreement.

However, one strength of the protocol as a result of the large number of fields is that the analysis is broad enough to identify trends in skill execution and injury aetiology which, conceivably, should enable it to be a useful tool in the attempt to refine the focus of future research to identify injury aetiology in the tackle. The discussion in section 7.3 suggests that there is potential for this outcome to be realised. The large number of fields also allows for the internal consistency of the protocol to be monitored and it is hoped that this will lead to a reduction in errors. An additional advantage is that the protocol allows flexibility for subsequent analyses to be focussed according to the requirements of the research, such that some fields may not be used in all analyses, or specific aspects, such as ground contact, can be targeted.

A number of limitations of this study could be used to inform future studies with similar aims. The use, and limitation, of percentage of agreement as the primary indicator of agreement has been previously discussed in section 8.3. It is conceivable that using two groups of raters from distinctly different areas, as was the case between the Australian and UK based participants in IRR1, will also serve to limit chance agreement. While the use of two participant groups may have been an advantage for IRR1, it was unfortunate that the UK based participants were unavailable for the second IRR study. It is possible that improvements in agreement that were observed between the two studies may be a result of this methodological difference. To partially address this, the IRR2 was conducted 12 months after IRR1 in the Australian based participants to reduce learning effects that may have occurred. Future investigations of reliability should try to maintain a constant pool of participants from which raters of each target may be drawn.

198 The use of an ‘unsure’ field variable, in many fields that would otherwise be dichotomous, reduces the likelihood that raters will make a guess to provide a definitive answer and contributes to a reduction in agreement expected through chance. It could also potentially bias the results as the response (‘unsure’) is subjective and dependent upon the individual that is rating the event. Should future research include ‘unsure’ field variables, the frequency of use should be monitored and carefully considered as an additional component of agreement, as presented in Chapter Seven (Table 7.2). A high number of unsure responses within a field may indicate that the field must be revisited to increase reliability and validity.

The primary strength of this research has been the development of the protocol, which attempted to incorporate information from a number of existing methods and theoretical frameworks. For the most part, research using qualitative technique analysis has not described the process of developing the analysis protocol, making this work unique. It has been observed that many qualitative technique analysis studies in sports science did not assess agreement numerically, while ergonomic and clinical research routinely used only one phase of reliability testing. This research used two phases of reliability testing to assess agreement and incorporated a formal process to improve agreement.

199 8.6 Conclusions

This thesis represents an attempt to develop a reliable and valid qualitative analysis protocol to assess skill execution and injury risk in the tackle in rugby union. The results of the application of the protocol to a sample of tackles, its use in two studies examining injury risk in the tackle, suggest that the protocol provides a valid instrument for this purpose (Fuller, et al., 2010; McIntosh, Savage, et al., 2010), and supports that observable aspects of skill and injury risk have been successfully identified, addressing the first two questions that were nominated for this research. Developing the qualitative analysis protocol was a time consuming process. As this thesis has demonstrated, the bulk of the development process involved identifying research to collect relevant empirical data on which the protocol could be based and then developing means by which these features could be assessed. In the absence of a suitable method of analysis, this was necessary.

Reliability testing of the tackle analysis protocol identified a number of limitations of this method. Some of the attempts to improve these limitations were successful, and the general agreement for the protocol improved following the changes that were made between IRR1 and IRR2. It cannot be stated with certainty that the protocol will be found to be reliable in all situations. The remaining limitations, particularly agreement of the tackle type field, should be considered during any research utilising this, or any other, qualitative analysis protocol. A number of suggestions have been made regarding the operationalisation of the protocol to minimise limitations.

The protocol that was developed here represents a model that may now be updated and altered by future research as new injury concerns arise or statistical methods arise. Similarly, it is hoped that this research presents a useful framework for developing a reliable qualitative analysis method through a systematic and repeatable process that can also be used and built upon by future research.

200 REFERENCES

"Aetiology" (2010) Oxford English Dictionary. Edited by Angus Stevenson. (2nd ed., rev.). Oxford: Oxford University Press. Adams, I. D. (1977). Rugby football injuries. British Journal of Sports Medicine, 11(1), 4-6. Addley, K., & Farren, J. (1988). Irish rugby injury survey: Dungannon Football Club (1986-87). British Journal of Sports Medicine, 22(1), 22-24. Alsop, J. C., Morrison, L., Williams, S. M., Chalmers, D. J., & Simpson, J. C. (2005). Playing conditions, player preparation and rugby injury : a case- control study. Journal of Science & Medicine in Sport, 8(2), 171-180. Andersen, T. E., Engebretsen, L., & Bahr, R. (2004). Rule violations as a cause of injuries in male norwegian professional football: are the referees doing their job? American Journal of Sports Medicine, 32(1 Suppl), 62S-68S. Andersen, T. E., Floerenes, T. W., Arnason, A., & Bahr, R. (2004). Video analysis of the mechanisms for ankle injuries in football. American Journal of Sports Medicine, 32(1 Suppl), 69S-79S. Andersen, T. E., Larsen, O., Tenga, A., Engebretsen, L., & Bahr, R. (2003). Football incident analysis: a new video based method to describe injury mechanisms in professional football. British Journal of Sports Medicine, 37(3), 226-232. Andersen, T. E., Tenga, A., Engebretsen, L., & Bahr, R. (2004). Video analysis of injuries and incidents in Norwegian professional football. British Journal of Sports Medicine, 38(5), 626-631. Appleby, B., & Dawson, B. (2002). Video analysis of selected game activities in Australian rules football. Journal of Science & Medicine in Sport, 5(2), 129-142. Archibald, R. M. (1962). An analysis of rugby football injuries in the 1961-62 season. Practitioner 189, 333-334. Arend, S., & Higgins, J. R. (1976). A strategy for the classification, subjective analysis and observation of human movement. Journal of Human Movement Studies, 2(1), 36-52. ARU. (2006a). ARU Smart Rugby: Confidence in contact. A guide to the smart rugby program. Sydney: Australian Rugby Union. ARU. (2006b). ARU Smart Rugby: interactive CD Rom. Sydney: Australian Rugby Union. Australian Bureau of Statistics. (1998). 1997 - 98 Participation in Sport and Physical Activities Australia. Cat. No. 4177.0., Canberra: ABS. Australian Bureau of Statistics. (2010). 2009 - 10 Participation in Sport and Physical Recreation Australia. Cat. No. 4177.0, Canberra: ABS.

201 Babic, Z., Misigoj-Durakovic, M., Matasic, H., & Jancic, J. (2001). Croatian rugby project. Part II: injuries. Journal of Sports Medicine & Physical Fitness, 41(3), 392-398. Bahr, R. (2001). Recent advances: Sports medicine. British Medical Journal, 323(7308), 328-331. Bahr, R., & Krosshaug, T. (2005). Understanding injury mechanisms: a key component of preventing injuries in sport. British Journal of Sports Medicine, 39(6), 324-329. Baluyut, R., Genaidy, A. M., Davis, L. S., Shell, R. L., & Simmons, R. L. (1995). Use of visual perception in estimating static postural stresses: magnitudes and sources of errors. Ergonomics, 38(9), 1841-1850. Barone, M., Senner, V., & Schaff, P. (1999). ACL injury mechanism in alpine skiing: analysis of an accidental ACL rupture. In R. J. Johnson (Ed.), Skiing Trauma and Safety (12 ed., pp. 63-81). West Conshohocken, PA: American Society for Testing and Materials. Bartlett, R. M. (2008). Introduction. In C. J. Payton & R. M. Bartlett (Eds.), Biomechanical evaluation of movement in sport and exercise: the British Association of Sport and Exercise Sciences guidelines (pp. 1 - 7). New York: Routledge. Bathgate, A., Best, J. P., Craig, G., & Jamieson, M. (2002). A prospective study of injuries to elite Australian rugby union players. British Journal of Sports Medicine, 36(4), 265-269. Bauman, A. E. (2004). Updating the evidence that physical activity is good for health: an epidemiological review 2000-2003. Journal of Science & Medicine in Sport, 7(1 Suppl), 6-19. Best, J. P., McIntosh, A. S., & Savage, T. N. (2005). Rugby World Cup 2003 Injury Surveillance Project. British Journal of Sports Medicine, 39(11), 812 - 817. Bird, Y. N., Waller, A. E., Marshall, S. W., Alsop, J. C., Chalmers, D. J., & Gerrard, D. F. (1998). The New Zealand Rugby Injury and Performance Project: V. Epidemiology of a season of rugby injury. British Journal of Sports Medicine, 32(4), 319-325. Boden, B. P. (2005). Direct catastrophic injury in sports. [Review]. The Journal of the American Academy of Orthopaedic Surgeons, 13(7), 445-454. Bohu, Y., Julia, M., Bagate, C., Peyrin, J. C., Colonna, J. P., Thoreux, P., et al. (2009). Declining incidence of catastrophic cervical spine injuries in French rugby: 1996-2006. American Journal of Sports Medicine, 37(2), 319-323. Boufous, S., Finch, C., & Bauman, A. (2004). Parental safety concerns - a barrier to sport and physical activity in children? Australian and New Zealand Journal of Public Health 28(5), 482-486.

202 Brooks, J. H. M., & Fuller, C. W. (2006). The Influence of Methodological Issues on the Results and Conclusions from Epidemiological Studies of Sports Injuries: Illustrative Examples. [Opinion]. Sports Medicine, 36(6), 459-472. Brooks, J. H. M., Fuller, C. W., Kemp, S. P. T., & Reddin, D. B. (2005a). Epidemiology of injuries in English professional rugby union: part 1 match injuries. British Journal of Sports Medicine, 39(10), 757-766. Brooks, J. H. M., Fuller, C. W., Kemp, S. P. T., & Reddin, D. B. (2005b). Epidemiology of injuries in English professional rugby union: part 2 training Injuries. British Journal of Sports Medicine, 39(10), 767-775. Brooks, J. H. M., Fuller, C. W., Kemp, S. P. T., & Reddin, D. B. (2005c). A prospective study of injuries and training amongst the England 2003 Rugby World Cup squad. British Journal of Sports Medicine, 39(5), 288-293. Browne, G. J. (2006). Cervical spinal injury in children's community rugby football. British Journal of Sports Medicine, 40(1), 68-71. Brunnekreef, J., van Uden, C., van Moorsel, S., & Kooloos, J. (2005). Reliability of videotaped observational gait analysis in patients with orthopedic impairments. BMC Musculoskeletal Disorders, 6(1), 17. Brunton, A., Ellis, B., & Goddard, J. (1999). Comparison of Visual Estimation and Goniometry for Assessment of Metacarpophalangea Joint Angle. Physiotherapy, 85(4), 201-208. Buckwalter, J. A. (2003). Sports, joint injury, and posttraumatic osteoarthritis. Journal of Orthopaedic & Sports Physical Therapy, 33(10), 578-588. Burry, H. C., & Gowland, H. (1981). Cervical injury in rugby football - a New Zealand survey. British Journal of Sports Medicine, 15(1), 56-59. Burt, C. D., Henningsen, N., & Consedine, N. (1999). Prompting correct lifting posture using signs. Applied Ergonomics, 30(4), 353-359. Burt, S., & Punnett, L. (1999). Evaluation of interrater reliability for posture observations in a field study. Applied Ergonomics, 30(2), 121-135. Carmody, D. J., Taylor, T. K. F., Parker, D. A., Coolican, M. R. J., & Cumming, R. G. (2005). Spinal cord injuries in Australian footballers 1997-2002. The Medical Journal of Australia, 182(11), 561-564. Chapman, P. J. (1985). The prevalence of orofacial injuries and use of mouthguards in Rugby Union. Australian Dental Journal, 30(5), 364-367. Clark, D. R., Roux, C., & Noakes, T. D. (1990). A prospective study of the incidence and nature of injuries to adult rugby players. South African Medical Journal, 77(11), 559-562. "Cause" (2010) Oxford English Dictionary. Edited by Angus Stevenson. (2nd ed., rev.). Oxford: Oxford University Press. Cohen, J. (1960). A coefficient for agreement for nominal scales. Educational and Psychological Measurement, 20(1), 37-46.

203 Cohen, J. (1968). Weighted kappa: Nominal scale agreement provision for scaled disagreement or partial credit. Psychological Bulletin, 70(4), 213. Cumps, E., Verhagen, E., Annemans, L., & Meeusen, R. (2008). Injury rate and socioeconomic costs resulting from sports injuries in Flanders: data derived from sports insurance statistics 2003. British Journal of Sports Medicine, 42(9), 767-772. Dallalana, R. J., Brooks, J. H., Kemp, S. P., & Williams, A. M. (2007). The epidemiology of knee injuries in English professional rugby union. American Journal of Sports Medicine, 35(5), 818-830. Dartt, A., Rosecrance, J., Gerr, F., Chen, P., Anton, D., & Merlino, L. (2009). Reliability of assessing upper limb postures among workers performing manufacturing tasks. Applied Ergonomics, 40(3), 371-378. David, G., Woods, V., Li, G., & Buckle, P. (2008). The development of the Quick Exposure Check (QEC) for assessing exposure to risk factors for work-related musculoskeletal disorders. Applied Ergonomics, 39(1), 57-69. Davidson, R. M. (1987). Schoolboy rugby injuries, 1969-1986. The Medical Journal of Australia, 147(3), 119-120. Davidson, R. M., Kennedy, M., Kennedy, J., & Vanderfield, G. (1978). Casualty room presentations and schoolboy rugby union. The Medical Journal of Australia, 1(5), 247-249. Davies, J. E., & Gibson, T. (1978). Injuries in rugby union football. British Medical Journal, 2(6154), 1759-1761. Davies, R. M., Bradley, D., Hale, R. W., Laired, W. R., and Thomas, P. D. (1977). Prevalence of dental injuries in rugby players and their attitude to mouthguards. British Journal of Sports Medicine, 11(2), 72-74. Deutsch, M. U., Maw, G. J., Jenkins, D., & Reaburn, P. (1998). Heart rate, blood lactate and kinematic data of elite colts (under-19) rugby union players during competition. Journal of Sports Sciences, 16(6), 561-570. Docherty, D., Wenger, H., & Neary, P. (1988). Time-motion analysis related to the physiological demands of rugby. Journal of Human Movement Studies, 14(6), 269–277. Durie, R. M., & Munroe, A. D. (2000). A prospective survey of injuries in a New Zealand schoolboy rugby population. New Zealand Journal of Sports Medicine, 28(4), 84-90. Duthie, G., Pyne, D., & Hooper, S. (2003a). Applied physiology and game analysis of rugby union. Sports Medicine, 33(13), 973-991. Duthie, G., Pyne, D., & Hooper, S. (2003b). The reliability of video based time motion analysis. Journal of Human Movement Studies, 44(4), 259-271. Duthie, G., Pyne, D., & Hooper, S. (2005). Time motion analysis of 2001 and 2002 super 12 rugby. Journal of Sports Sciences, 23(5), 523-530.

204 Elliott, B., & Wood, G. A. (1995). Biomechanical principles. In J. Bloomfield, P. A. Fricker & K. D. Fitch (Eds.), Science and Medicine in Sport. Carlton: Blackwell Science. Finch, C. F., Boufous, S., & Dennis, R. (2007). Sport/leisure injury hospitalisation episodes in NSW, 2003-2004: Sociodemographic and geographic patterns and sport-specific profiles. Sydney: NSW Injury Risk Management Research Centre, UNSW. Finch, C. F., Valuri, G., & Ozanne-Smith, J. (1998). Sport and active recreation injuries in Australia: evidence from emergency department presentations British Journal of Sports Medicine, 32(3), 220-225. Fleiss, J. L. (1971). Measuring nominal scale agreement among many raters. Psychological Bulletin, 76(5), 378-372. Franks, I. M. (1993). The effects of experience on the detection and location of performance differences in a gymnastic technique. Research Quarterly for Exercise and Sport, 64(2), 227-231. Fréchède, B. O., & McIntosh, A. S. (2009). Numerical reconstruction of real-life concussive football impacts. Medicine and Science in Sport and Exercise, 41(2), 390. Fuller, C. W., Ashton, T., Brooks, J. H., Cancea, R. J., Hall, J., & Kemp, S. P. (2010). Injury risks associated with tackling in rugby union. British Journal of Sports Medicine, 44(4), 159-167. Fuller, C. W., Brooks, J. H. M., Cancea, R. J., Hall, J., & Kemp, S. P. T. (2007). Contact events in rugby union and their propensity to cause injury. British Journal of Sports Medicine, 41(12), 862-867. Fuller, C. W., Ekstrand, J., Junge, A., Andersen, T. E., Bahr, R., Dvorak, J., et al. (2006). Consensus statement on injury definitions and data collection procedures in studies of football (soccer) injuries. British Journal of Sports Medicine, 40(3), 193-201. Fuller, C. W., Junge, A., & Dvorak, J. (2004). An assessment of football referees' decisions in incidents leading to player injuries. American Journal of Sports Medicine, 32(1 Suppl), 17S-22S. Fuller, C. W., Molloy, M. G., Bagate, C., Bahr, R., Brooks, J. H., Donson, H., et al. (2007). Consensus statement on injury definitions and data collection procedures for studies of injuries in rugby union. British Journal of Sports Medicine, 41(5), 328-331. Fuller, C. W., Smith, G. L., Junge, A., & Dvorak, J. (2004). An assessment of player error as an injury causation factor in international football. American Journal of Sports Medicine, 32(1 Suppl), 28S-35S. Gabbett, T. J. (2004). Incidence of injury in junior and senior rugby league players. Sports Medicine, 34(12), 849-859.

205 Garraway, W. M., Lee, A. J., Hutton, S. J., Russell, E. B. A. W., & Macleod, D. A. D. (2000). Impact of professionalism on injuries in rugby union. British Journal of Sports Medicine 34(5), 348-351. Garraway, W. M., Lee, A. J., Macleod, D. A. D., Telfer, J. W., Deary, I. J., & Murray, G. D. (1999). Factors influencing tackle injuries in rugby union football. British Journal of Sports Medicine 33(1), 37-41. Garraway, W. M., & Macleod, D. A. D. (1995). Epidemiology of rugby football injuries. Lancet, 345(8963), 1485-1487. Gissane, C., Jennings, D., Kerr, K., & White, J. A. (2002). A pooled data analysis of injury incidence in rugby league football. Sports Medicine, 32(3), 211-216. Grant, S. J., Oommen, G., McColl, G., Taylor, J., Watkins, L., Friel, N., et al. (2003). The effect of ball carrying method on sprint speed in rugby union football players. Journal of Sports Sciences, 21(12), 1009-1015. Grayson, E. (1996). Medicolegal aspects of deliberate foul play in rugby union. British Journal of Sports Medicine, 30(3), 191-192. Greenfield, B. H., Greene, B., & Johanson, M. A. (2007). The use of qualitative research techniques in orthopedic and sports physical therapy: Moving toward postpositivism. Physical Therapy in Sport, 8(1), 44-54. Haddon, W. (1999). The changing approach to the epidemiology, prevention, and amelioration of trauma: the transition to approaches etiologically rather than descriptively based. 1968. Injury Prevention, 5(3), 231-235. Hagel, B., & Meeuwisse, W. H. (2004). Risk Compensation: A “Side Effect” of Sport Injury Prevention? [Editorial]. Clinical Journal of Sport Medicine, 14(4), 193-196. Hall, S. J. (2006). Basic biomechanics (5th ed.). Sydney: McGraw-Hill. Hamill, J., & Knutzen, K. M. (1995). Biomechanical Basis of Human Movement. Baltimore: Lippincott Williams & Wilkins. Hay, J. G. (1993). The Biomechanics of Sports Techniques (4th ed.). Sydney: Prentice Hall. Hay, J. G., & Reid, J. G. (1988). Anatomy, Mechanics and Human motion (2nd ed.). Sydney: Prentice-Hall. Headey, J., Brooks, J. H., & Kemp, S. P. (2007). The epidemiology of shoulder injuries in English professional rugby union. American Journal of Sports Medicine, 35(9), 1537-1543. Hoelen, M. A., Burgers, A. M., & Rozing, P. M. (1990). Prognosis of primary anterior shoulder dislocation in young adults. Archives of Orthopaedic and Trauma Surgery, 110(1), 51-54. Holmefur, M., Krumlinde-Sundholm, L., & Eliasson, A. C. (2007). Interrater and intrarater reliability of the Assisting Hand Assessment. The American Journal of Occupational Therapy, 61(1), 79.

206 Hughes, D. C., & Fricker, P. A. (1994). A prospective survey of injuries to first- grade rugby union football players. Clinical Journal of Sport Medicine, 4(4), 249-256. Hughes, M. D., & Bartlett, R. M. (2002). The use of performance indicators in performance analysis. Journal of Sports Sciences, 20(10), 739-754. Hulstyn, M. J., & Fadale, P. D. (1997). Shoulder injuries in the athlete. [Review]. Clinics in Sports Medicine, 16(4), 663-679. Inglis, G. S., & Stewart, I. D. (1981). Rugby injury survey 1979. New Zealand Medical Journal, 94(695), 349-350. International Rugby Board. (2004). IRB Strategic Plan. Dublin: IRB. International Rugby Board. (2005a). Changes in playing of international rugby over a 20 year period. Dublin: IRB. International Rugby Board. (2005b). The Laws of the game of Rugby Union 2005. Dublin: IRB. International Rugby Board. (2005c). Playing charter. Dublin: IRB. International Rugby Board. (2007). Year in Review: 2007. Dublin: IRB. International Rugby Board. (2008). A beginner's guide to rugby union. Dublin: IRB. International Rugby Board. (2010). The laws of the game of rugby union 2010. Dublin: IRB. Jones, S. J., Lyons, R. A., Evans, R., Newcombe, R. G., & Palmer, S. R. (2003). Do scrum caps reduce head and facial injuries to rugby players? A case control and video cohort study. Journal of Sports Sciences, 21(4), 278- 279. Junge, A. (2000). The influence of psychological factors on sports injuries. Review of the literature. American Journal of Sports Medicine, 28(5 Suppl), S10- S15. Junge, A., Cheung, K., Edwards, T., & Dvorak, J. (2004). Injuries in youth amateur soccer and rugby players - comparison of incidence and characteristics. British Journal of Sports Medicine 38(2), 168-172. Keenan, A., & Bach, T. (1996). Video assessment of rearfoot movements during walking: A reliability study. Archives of Physical Medicine and Rehabilitation, 77(7), 651-655. Ketola, R., Toivonen, R., & Viikari-Juntura, E. (2001). Interobserver repeatability and validity of an observation method to assess physical loads imposed on the upper extremities. Ergonomics, 44(2), 119-131. Kibler, W., Uhl, T., Maddux, J., Brooks, P., Zeller, B., & McMullen, J. (2002). Qualitative clinical evaluation of scapular dysfunction: a reliability study. Journal of Shoulder and Elbow Surgery, 11(6), 550-556.

207 Kibler, W. B. (2001). Shoulder Pain. In P. Brukner & K. Khan (Eds.), Clinical Sports Medicine (2nd ed., pp. 229–273). Sydney: McGraw Hill. Kirkwood, B. R., & Sterne, J. A. C. (2003). Essential medical statistics (2nd ed.). Carlton: Wiley-Blackwell. Klügl, M., Shrier, I., McBain, K., Shultz, R., Meeuwisse, W. H., Garza, D., et al. (2010). The prevention of sport injury: an analysis of 12 000 published manuscripts. Clinical Journal of Sport Medicine, 20(6), 407. Knudson, D. V. (1999). Validity and reliability of visual ratings of the vertical jump. Perceptual and Motor Skills, 89(2), 642-648. Knudson, D. V. (2000). Qualitative analysis: Putting it all together. What can professionals qualitatively analyse? Journal of Physical Education, Recreation and Dance, 71(2), 19-23. Knudson, D. V., & Morrison, C. (1996). An integrated qualitative analysis of overarm throwing. Journal of Physical Education, Recreation & Dance, 67(6), 31-37. Knudson, D. V., & Morrison, C. S. (2002). Qualitative analysis of human movement (2nd ed.). Lower Mitcham: Human Kinetics. Koh, J. O., & Watkinson, E. J. (2002). Video analysis of blows to the head and face at the 1999 World Taekwondo Championships. Journal of Sports Medicine and Physical Fitness, 42(3), 348-353. Kreighbaum, E., & Barthels, K. M. (1996). Biomechanics: A Qualitative Approach for Studying Human Movement (4th ed.). Sydney: Allyn and Bacon. Kroner, K., Lind, T., & Jensen, J. (1989). The epidemiology of shoulder dislocations. Archives of Orthopaedic and Trauma Surgery, 108(5), 288- 290. Krosshaug, T., Andersen, T. E., Olsen, O. E. O., Myklebust, G., & Bahr, R. (2005). Research approaches to describe the mechanisms of injuries in sport: limitations and possibilities. British Journal of Sports Medicine, 39(6), 330-339. Krosshaug, T., Nakamae, A., Boden, B., Engebretsen, L., Smith, G., Slauterbeck, J., et al. (2007). Estimating 3D joint kinematics from video sequences of running and cutting maneuvers - assessing the accuracy of simple visual inspection. Gait and Posture, 26(3), 378-385. Kuriyama, S., Fujimaki, E., Katagiri, T., & Uemura, S. (1984). Anterior dislocation of the shoulder joint sustained through skiing : Arthrographic findings and prognosis. American Journal of Sports Medicine, 12(5), 339- 346. Landis, J. R., & Koch, G. G. (1977). The measurement of observer agreement for categorical data. Biometrics, 33(1), 159-174.

208 Lee, A. J., & Garraway, W. M. (1996). Epidemiological comparison of injuries in school and senior club rugby. British Journal of Sports Medicine, 30(3), 213-217. Lee, A. J., & Garraway, W. M. (2000). The influence of environmental factors on rugby football injuries. Journal of Sports Sciences, 18(2), 91-95 Lees, A. (2002). Technique analysis in sports: a critical review. Journal of Sports Sciences, 20(10), 813-828. Lemos, M. J. (1998). The evaluation and treatment of the injured acromioclavicular joint in athletes. American Journal of Sports Medicine, 26(1), 137-144. Liebermann, D. G., & Franks, I. M. (2008). Video Feedback and Information technologies. In M. Hughes & I. M. Franks (Eds.), The essentials of performance analysis: an introduction (pp. 40 - 50). New York: Routledge. Lloyd, D. G., & Besier, T. F. (2003). An EMG-driven musculoskeletal model to estimate muscle forces and knee joint moments in vivo. Journal of Biomechanics, 36(6), 765-776. Magill, R. A. (1998). Motor Learning: Concepts and Applications (5th ed.). Boston, Massachusetts: McGraw Hill. Marshall, R. N., & Elliott, B. C. (1995). Biomechanical Analysis. In J. Bloomfield, P. A. Fricker & K. D. Fitch (Eds.), Science and Medicine in Sport (2nd ed.). Carlton: Blackwell Science. Maslovat, D., & Franks, I. M. (2008). The need for feedback. In M. Hughes & I. M. Franks (Eds.), The essentials of performance analysis: an introduction (pp. 1 - 7). New York: Routledge. McAtamney, L., & Nigel Corlett, E. (1993). RULA: a survey method for the investigation of work-related upper limb disorders. Applied Ergonomics, 24(2), 91-99. McCrory, P. (1998). Neurological injuries in rugby and Australian rules football. In T. P. Jordan B., Warren R. (Ed.), Sports Neurology (2nd ed., pp. 441- 449). Philadelphia: Lippincott-Raven Publishers. McGraw, K. O., & Wong, S. P. (1996). Forming inferences about some intraclass correlation coefficients. Psychological Methods, 1(1), 30-46. McIntosh, A. S. (2005a). Risk compensation, motivation, injuries, and biomechanics in competitive sport. British Journal of Sports Medicine, 39 (1), 2-3. McIntosh, A. S. (2005b). Rugby injuries. Medicine and Sport Science, 49, 120- 139. McIntosh, A. S., Best, J. P., Orchard, J., & Savage, T. N. (2004). Rugby Union Injury Surveillance Study: Report on Seasons 2000-2002 (Report). Sydney: The University of New South Wales.

209 McIntosh, A. S., McCrory, P., Finch, C. F., Best, J. P., & Chalmers, D. J. (2005). Rugby Headgear Study - Final Report. Sydney: The University of New South Wales. McIntosh, A. S., McCrory, P., Finch, C. F., & Wolfe, R. (2010). Head, face and neck injury in youth rugby: incidence and risk factors. British Journal of Sports Medicine, 44(3), 188-193. McIntosh, A. S., & Savage, T. N. (2005). Rugby Union Injury Surveillance Study: Report on Seasons 2002-2004. Sydney: The University of New South Wales. McIntosh, A. S., Savage, T. N., & Dutfield, R. L. (2008). Rugby Union Injury Surveillance Study: Report on Seasons 2004-2006. Sydney: The University of New South Wales. McIntosh, A. S., Savage, T. N., McCrory, P., Fréchède, B. O., & Wolfe, R. (2010). Tackle characteristics and injury in a cross section of rugby union football. Medicine and Science in Sport and Exercise, 42(5), 977-984. McIntosh, A. S., Savage, T. N., & Nicholson, A. (2005). Investigating the Tackle in Rugby Union. Paper presented at the Australian Conference of Science and Medicine in Sport. McLean, D. A. (1992). Analysis of the physical demands of international rugby union. Journal of Sports Sciences, 10(3), 285-296. McManus, A., & Cross, D. S. (2004). Incidence of injury in elite junior rugby union: a prospective descriptive study. Journal of Science & Medicine in Sport, 7(4), 438-445. McPherson, M. N. (1996). Qualitative and quantitative analysis in sports. American Journal of Sports Medicine, 24(6 Suppl), S85. Meeuwisse, W. H. (1994). Assessing Causation in Sport Injury: A Multifactorial Model. Clinical Journal of Sport Medicine, 4(3), 166-170. Meeuwisse, W. H., Tyreman, H., Hagel, B., & Emery, C. (2007). A dynamic model of ætiology in sport injury: the recursive nature of risk and causation. Clinical Journal of Sport Medicine, 17(3), 215-219. Milburn, P. D. (1990). The kinetics of rugby union scrummaging. Journal of Sports Sciences, 8(1), 47-60. Milburn, P. D. (1993). Biomechanics of rugby union scrummaging. Technical and safety issues. Sports Medicine, 16(3), 168-179. Nathan, M., Goedeke, R., & Noakes, T. D. (1983). The incidence and nature of rugby injuries experienced at one school during the 1982 rugby season. South African Medical Journal, 64(4), 132-137. Noonan, K., Halliday, S., Browne, R., O'Brien, S., Kayes, K., & Feinberg, J. (2003). Interobserver variability of gait analysis in patients with cerebral palsy. Journal of Pediatric Orthopaedics, 23(3), 279.

210 Norton, K., Schwerdt, S., & Lange, K. (2001). Evidence for the aetiology of injuries in Australian football. British Journal of Sports Medicine, 35(6), 418-423. NZRU, & ACC. (2005a). 2005 Rugby Smart: A guide to injury prevention for peak performance: New Zealand Rugby Union. NZRU, & ACC. (2005b). 2005 Rugby Smart: A guide to injury prevention for peak performance: New Zealand Rugby Union. O'Brien, C. P. (1996). "Rugby neck": cervical degeneration in two front row rugby union players. Clinical Journal of Sport Medicine, 6(1), 56-59. Oehlert, K., Drescher, W., Petersen, W., Zantop, T., Gross, V., & Hassenpflug, J. (2004). [Injuries in Olympic handball tournaments: a video analysis]. Sportverletzung Sportschaden, 18(2), 80-84. Olsen, O. E., Myklebust, G., Engebretsen, L., & Bahr, R. (2004). Injury mechanisms for anterior cruciate ligament injuries in team handball: a systematic video analysis. American Journal of Sports Medicine, 32(4), 1002-1012. Orchard, J. (2002). Is there a relationship between ground and climatic conditions and injuries in football? Sports Medicine, 32(7), 419-432. Orchard, J., James, T., Alcott, E., Carter, S., & Farhart, P. (2002). Injuries in Australian cricket at first class level 1995/1996 to 2000/2001. British Journal of Sports Medicine, 36(4), 270. Orchard, J., Newman, D., Stretch, R., Frost, W., Mansingh, A., & Leipus, A. (2005). Methods for injury surveillance in international cricket. Journal of Science and Medicine in Sport, 8(1), 1-14. Orchard, J., & Seward, H. (2002). Epidemiology of injuries in the Australian Football League, seasons 1997–2000. British Journal of Sports Medicine, 36(1), 39. Orchard, J., Seward, H., McGivern, J., & Hood, S. (2001). Intrinsic and extrinsic risk factors for anterior cruciate ligament injury in Australian footballers. American Journal of Sports Medicine, 29(2), 196. Pain, M. T., Tsui, F., & Cove, S. (2008). In vivo determination of the effect of shoulder pads on tackling forces in rugby. Journal of Sports Sciences, 26(8), 855-862. Patton, M. Q. (1999). Enhancing the quality and credibility of qualitative analysis. Health Services Research, 34(5 Pt 2), 1189-1208. Patton, M. Q. (2002). Qualitative evaluation and research methods (3rd ed.). London: Sage Publications. Payton, C. J. (2007). Motion analysis using video. In C. J. Payton & R. M. Bartlett (Eds.), Biomechanical evaluation of movement in sport and exercise: the British Association of Sport and Exercise Sciences guidelines (pp. 8 - 32). New York: Routledge.

211 Pellman, E. J., Viano, D. C., Tucker, A. M., Casson, I. R., & Waeckerle, J. F. (2003). Concussion in professional football: Reconstruction of game impacts and injuries. Neurosurgery, 53(4), 799. Powers, P. N. R., & Harrison, A. J. (1999). Models for biomechanical analysis of jumping horses. Journal of Equine Veterinary Science, 19(12), 799. Quarrie, K. L., Cantu, R. C., & Chalmers, D. J. (2002). Rugby union injuries to the cervical spine and spinal cord. Sports Medicine, 32(10), 633-653. Quarrie, K. L., Gianotti, S. M., Chalmers, D. J., & Hopkins, W. G. (2005). An evaluation of mouthguard requirements and dental injuries in New Zealand rugby union. British Journal of Sports Medicine, 39(9), 650-651. Quarrie, K. L., Gianotti, S. M., Hopkins, W. G., & Hume, P. A. (2007). Effect of nationwide injury prevention programme on serious spinal injuries in New Zealand rugby union: ecological study. British Medical Journal, 334(7604), 1150-1153. Quarrie, K. L., & Hopkins, W. (2007). Changes in Player Characteristics and Match Activities in Bledisloe Cup Rugby Union from 1972 to 2004. Journal of Sports Sciences, 25(8), 895-903. Quarrie, K. L., & Hopkins, W. G. (2008). Tackle injuries in professional Rugby Union. American Journal of Sports Medicine, 36(9), 1705-1716. Quarrie, K. L., & Wilson, B. D. (2000). Force production in the rugby union scrum. Journal of Sports Sciences, 18(4), 237-246. Raftery, M., Parker, R., Stacey, E., Peat, J., & Wang, H. (1999). Incidence of injury in junior rugby league in the Penrith and District junior rugby league area. Westmead: Children's Hospital Institute of Sports Medicine, Research and Development Office.

Read, H. S., Hazlewood, M. E., Hillman, S. J., Prescott, R. J., & Robb, J. E. (2003). Edinburgh visual gait score for use in cerebral palsy. Journal of Pediatric Orthopaedics, 23(3), 296-301. Rotem, T. R., Lawson, J. S., Wilson, S. F., Engel, S., Rutkowski, S. B., & Aisbett, C. W. (1998). Severe cervical spinal cord injuries related to rugby union and league football in New South Wales, 1984-1996. The Medical Journal of Australia, 168(8), 379-381. Roux, C. E., Goedeke, R., Visser, G. R., van Zyl, W. A., & Noakes, T. D. (1987). The epidemiology of schoolboy rugby injuries. South African Medical Journal, 71(5), 307-317. Scher, A. T. (1977). Rugby injuries to the cervical spinal cord. South African Medical Journal, 51(14), 473-475. Scher, A. T. (1978). The high rugby tackle: an avoidable cause of cervical spinal injury? South African Medical Journal, 53(25), 1015-1018.

212 Scher, A. T. (1981). Vertex impact and cervical dislocation in rugby players. South African Medical Journal, 59(7), 227-228. Scher, A. T. (1983a). The 'double tackle' - another cause of serious cervical spinal injury in rugby players. South African Medical Journal, 64(15), 595-596. Scher, A. T. (1983b). Rugby injuries of the upper cervical spine. Case reports. South African Medical Journal, 64(12), 456-458. Scher, A. T. (1991a). Catastrophic rugby injuries of the spinal cord: changing patterns of injury. British Journal of Sports Medicine, 25(1), 57-60. Scher, A. T. (1991b). Paralysis due to the high tackle: a black spot in South African rugby. South African Medical Journal, 79(10), 614-615. Schwartz, M., Trost, J., & Wervey, R. (2004). Measurement and management of errors in quantitative gait data. Gait and Posture, 20(2), 196-203. Shephard, R. J. (1995). Exercise and cancer: linkages with obesity? International Journal of Obesity and Related Metabolic Disorders, 19 (4 Suppl), S62-S68. Shewchenko, N., Withnall, C., Keown, M., Gittens, R., & Dvorak, J. (2005). Heading in football. Part 2: biomechanics of ball heading and head response. British Journal of Sports Medicine, 39(1 Suppl), i26. Shrout, P. E., & Fleiss, J. L. (1979). Intraclass correlations: uses in assessing rater reliabillity. Psychological Bulletin, 86(2), 420-428. Silver, J. R., & Gill, S. (1988). Injuries of the spine sustained during rugby. Sports Medicine, 5(5), 328-334. Smart, D. J., Gill, N. D., Beaven, C. M., Cook, C. J., & Blazevich, A. J. (2008). The relationship between changes in interstitial creatine kinase and game- related impacts in rugby union. British Journal of Sports Medicine, 42(2), 198-201. Sofaer, S. (1999). Qualitative methods: What are they and why use them? Health Services Research, 34(5 pt 2), 1101 - 1118. Sovio, O. M., van Peteghem, P. K., & Schweigel, J. F. (1984). Cervical spine injuries in rugby players. Canadian Medical Association Journal, 130(6), 735-736. Sparks, J. P. (1981). Half a million hours of rugby football. The injuries. British Journal of Sports Medicine, 15(1), 30-32. "Tackle" (2005) Oxford English Dictionary. Edited by Angus Stevenson. (2nd ed., rev.). Oxford: Oxford University Press. Takarada, Y. (2003). Evaluation of muscle damage after a rugby match with special reference to tackle plays. British Journal of Sports Medicine, 37 (5), 416-419. Takemura, M., Schneiders, A. G., Bell, M. L., & Milburn, P. D. (2007). Association of ground hardness with injuries in rugby union. British Journal of Sports Medicine, 41(9), 582-587; discussion 587.

213 Targett, S. G. (1998). Injuries in professional Rugby Union. Clinical Journal of Sport Medicine, 8(4), 280-285. Thomas, J. R., Nelson, J. K., & Silverman, S. J. (2005). Research methods in physical activity (5th ed.). Lower Mitcham: Human Kinetics. Trewartha, G., Casanova, R., & Wilson, C. (2008). A kinematic analysis of rugby lineout throwing. Journal of Sports Sciences, 26(8), 845-854. Trewartha, G., & Stokes, K. (2003). Impact forces during rugby tackles. Paper presented at the International Conference on the Science and Practice of Rugby, Brisbane, Australia. Twomey, D. M., Finch, C. F., Doyle, T. L. A., Elliott, B. C., & Lloyd, D. G. (2010). Level of agreement between field-based data collectors in a large scale injury prevention randomised controlled trial. Journal of Science and Medicine in Sport. Uebersax, J. S. (1987). Diversity of decision-making models and the measurement of interrater agreement. Psychological Bulletin, 101(1), 140. Uebersax, J. S. (2009). The Myth of Chance-Corrected Agreement Retrieved 1 December, 2010, from http://www.john-uebersax.com/stat/kappa2.htm Upson, N. (1982). Dental injuries and the attitudes of rugby players to mouthguards. British Journal of Sports Medicine, 16(4), 241-244. Usman, J., McIntosh, A. S., & Fréchède, B. O. (2011). An analysis of impact forces in an active shoulder tackle in rugby. British Journal of Sports Medicine, 45(4), 328. van Mechelen, W., Hlobil, H., & Kemper, H. C. G. (1992). Incidence, Severity, Aetiology and Prevention of Sports Injuries: A Review of Concepts. Sports Medicine, 14(2), 82 - 99. Viano, D. C., Casson, I. R., Pellman, E. J., Zhang, L., King, A. I., & Yang, K. H. (2005). Concussion in professional football: brain responses by finite element analysis: part 9. Neurosurgery, 57(5), 891. Walter, S. D., & Hart, L. E. (1990). Application of epidemiological methodology to sports and exercise science research. Exercise and Sport Sciences Reviews, 18(1), 417-448. Whitley, R., & Crawford, M. (2005). Qualitative research in psychiatry. Canadian Journal of Psychiatry - Revue Canadienne de Psychiatrie, 50(2), 108-114. Williams, J. P., & McKibbin, B. (1978). Cervical spine injuries in Rugby Union football. British Medical Journal, 2(6154), 1747. Wilson, B. D., Quarrie, K. L., Milburn, P. D., & Chalmers, D. J. (1999). The nature and circumstances of tackle injuries in rugby union. Journal of Science & Medicine in Sport, 2(2), 153-162. Zernicke, R. F., Garhammer, J., & Jobe, F. W. (1977). Human patellar-tendon rupture. Journal of Bone and Joint Surgery American Volume, 59(2), 179- 183.

214 LIST OF CONFERENCE PRESENTATIONS ARISING FROM

THIS RESEARCH

Invited symposia Savage, T. N., & McIntosh, A. S. (2008) Gross biomechanical description of injury situations in 2nd World Congress on Sports Injury Prevention. Tromsø, Norway.

Conference presentations Savage, T. N., McIntosh, A. S., Fréchède, B.O (2011). The development of a protocol to analyse the tackle in Rugby Union. Paper presented at the 3rd World Congress on Sports Injury Prevention. Monte Carlo, Monaco. Savage, T. N., & McIntosh, A. S. (2008). Tackling Characteristics in amateur and professional Rugby Union. Paper presented at the 8th World Congress of Performance Analysis in Sport. Magdeburg, Germany. McIntosh, A. S., Savage, T. N., Fréchède, B.O., Kemp, S.P.T. (2008). The development of a protocol to analyse the tackle in Rugby Union. Paper presented at the 8th World Congress of Performance Analysis in Sport. Magdeburg, Germany. Savage, T. N., McIntosh, A. S., Fréchède, B. O., & Kemp, S.P.T. (2007). Development of a method to assess injury risk factors associated with the tackle in Rugby Union. Paper presented at the Australian Conference of Science and Medicine in Sport. Adelaide, Australia. Savage, T. N., McIntosh, A. S., Kemp, S.P.T., & Fréchède, B. O. (2007). Developing a qualitative analysis protocol for the tackle in Rugby Union. Paper presented at the 6th Australasian Biomechanics Conference. Auckland, New Zealand.

215

216 APPENDICES

217

218 APPENDIX A

CODING MANUAL,INTER-RATER RELIABILITY

TESTING,PHASE 1

219

IRB Tackle study Inter Rater Reliability Study Tackle Analysis Coder Manual

Trevor Savage

July 2006

IRB Tackle Study:

Inter rater reliability study tackle coding manual STUDY BACKGROUND AND AIMS ...... 3 THE TACKLE SCHEMA ...... 4 TACKLE DEFINITION ...... 5 USING THE MACRO’S IN THE WORKBOOK...... 7 THE UPPER LEVEL:GENERIC TACKLE DESCRIPTORS ...... 8 Event type: ...... 9 Ball Carriers Club and Opposition Club: ...... 9 Counter ID: ...... 9 Phase of play before:...... 10 Tackle Type: ...... 10 Tackle complete/Is this an IRB Tackle: ...... 10 if no Why: ...... 10 Phase of play after:...... 11 Retains ball:...... 11 Number of tacklers:...... 11 Location information ...... 12 Field Half: ...... 12 Field Corridor:...... 12 Field Aisle:...... 13 Impact Force: ...... 13 Referees decision: ...... 13 Field and Match Conditions ...... 13 Ground Dry: ...... 13 Raining:...... 13 Was the player attempting to score: ...... 13 Position: ...... 13 Evasion technique: ...... 14 Tackle Outcome: ...... 14 Relative Height: ...... 14 Relative Mass:...... 15 Can this Tackle be coded further?...... 15 CODING TACKLES WITH TWO OR MORE PLAYERS...... 15 THE LOWER LEVEL:SPECIFIC TACKLE EVENT INFORMATION...... 16 Awarness, speed and body position:...... 17 Aware of the tackler:...... 17 Eyes on ball carrier: ...... 17 Was the ball carrier supported? ...... 17 Ball Carry Method: ...... 17 Speed of Ball Carrier:...... 17 Direction of travel: ...... 17 Body orientation of Ball Carrier...... 19 Leg drive, posture and footwork ...... 19 Back Straight:...... 19 Shoulders Rounded: ...... 19 Feet alignment:...... 19 Stance width/length:...... 20 Steps into tackle: ...... 20 Feet adjacent/Steps to base:...... 20 Knees bent:...... 20 Feet Preparation: ...... 20 Tackle Description: ...... 20 Tackle direction:...... 20 Arms Grapple:...... 21 Ball Carrier lifted by tackler:...... 21 Region Struck:...... 21 Head position in tackle...... 21 Head and neck flexion:...... 21 Body Posture:...... 21 Lower body position than Ball Carrier? ...... 21 Small steps in contact:...... 22 Direction after impact: ...... 22 Secondary impact with another tackler?...... 23 Inter rater study tackle coding manual 1-A

Ground Impact...... 24 Was there a ground impact for the Ball Carrier?...... 24 Striking object:...... 24 Final position of tackle:...... 24 Region loaded: ...... 24 Injury associated with ground impact?...... 25 Range of motion exceeded: ...... 25 Tackler contribute to the magnitude of load?...... 25 Limb motion retarded:...... 25 Loading pattern of main region affected: ...... 25 Specific factors:...... 25 Falling position: ...... 25 Falling: ...... 25 SUMMARY OF INSTRUCTIONS...... 26

2-A IRB Tackle study

Study background and aims Rugby union is a contact team sport with associated injury risks that are inherent to collisions and impact. In recent times, the focus of injury research has shifted to identification and monitoring, with the unions in Australia, England and New Zealand conducting ongoing injury surveillance studies to assess changes in rates of injury. In all of these studies, the tackle has been identified as the event associated most frequently with injury; accounting for between 40 and 50% of all rugby injuries. And while both the tackler/s and ball carrier can be injured in the tackle, this research has indicated that the ball carrier may be up to twice as likely to be injured in the tackle situation as the tackler.

Considering the high frequency of tackles (approximately 200 per game), it is not surprising that it is associated with a high proportion of injuries. However, when frequency is combined with body contact and the fall that may occur as a result, the risk of a serious joint injury, fracture or concussion increases. The International Rugby Board (IRB) is supporting the University of NSW (UNSW) and the Rugby Football Union (RFU) in their research of injury risks during the tackle. The aim of the research is to identify the characteristics of the tackle event (skill and technique) that are associated with injury risks. Specific aims include:

1. Investigate the aetiology of tackle related injuries 2. Investigate the specific characteristics of tackle skills and techniques related to injury causation 3. Assess using quantitative and qualitative biomechanical methods the tackles forces and compare these to injury outcomes 4. Assess the injury risks (frequency and consequences) associated with specific tackle skills 5. Provide guidelines for safe and effective tackles

As part of the funding agreements, RFU and UNSW researchers have been asked to collaborate on video analysis methods for the tackle.

Inter rater study tackle coding manual 3-A

The tackle schema During the last six months, research groups from the RFU and UNSW have been working to develop a series of criteria to classify tackles with the assistance and experience of coaching and officiating personnel. Each research group developed criteria independently, before combining the two methods to establish a schema to categorise the variables involved in tackle technique. While the populations and number of tackles that the two research groups are observing differ, the benefits of the development of a common schema, establishing a standard method of analysis and allowing comparison are clear. By applying the schema to a number of tackle events, including those that lead to injury and those that do not, factors and technique correlating with injury risk can be identified. This information could then be used in a subsequent study to develop a training program that encourages the development of safe and effective tackle skills appropriate for age and competition level.

) The first step is to test that the schema provides reliable and relevant information. You have been asked to participate in an inter rater reliability study of the video analysis schema. You will be asked to code pre-prepared video footage of tackles as well as identifying and coding any events which you would describe as tackles from two ten minute passages of play using the schema. The results of your coding will then be compared with those of other raters to identify the level of similarity between each rater.

4-A IRB Tackle study

Tackle definition A tackle could be generally described as a contact play in rugby union in which the opposition attempts to stop the ball carrier. Specifically, the IRB rule book defines the tackle as:

Law 15 A tackle occurs when the ball-carrier is held by one or more opponents and is brought to ground. A ball-carrier who is not held is not a tackled player and a tackle has not taken place. Opposition players who hold the ball-carrier and bring that player to ground, and who also go to ground, are known as tacklers. Opposition players who hold the ball-carrier and do not go to ground are not tacklers.

Thus under the IRB definition, if the ball carrier does not go to ground or if the player breaks through a ‘tackle contact’ then a tackle has not occurred. While strictly speaking this is correct, this rule serves as a reference base for phase’s of play which immediately follow a tackle such as rucks and mauls and many observers of the game would see any attempt to stop a player with the ball as a tackle. Therefore the definition set out in the Oxford English dictionary is more relevant:

5. (a) In Rugby, To seize and stop (an opponent) when in possession of the ball.

As this study is interested in examining how injuries occur in the tackle, you are asked to rate all incidents where you feel that the opponent (and thus ‘tackler’) is attempting to stop the ball carrier. Your analysis may include attempted tackles in which the ball carrier breaks through or evades the tackle, or ‘tackles’ in which the ball carrier is held up, amongst many other situations.

There are some exceptions that should not be coded:

Charge down events You should not code events where you feel an opponent was attempting to play at the ball rather than tackle the ball carrier. These will generally occur when the ball carrier has disposed of possession through kicking or passing and may include attempts to intercept a pass or charge down a kick.

The Maul Law 15.2 defines a maul as a situation when a tackle cannot take place (When the ball-carrier is held by one opponent and a team-mate binds on to that ball-carrier, a maul has been formed and a tackle cannot take place). In this case, you should code the first phase in which the ball carrier is stopped by one or more opponents, but not any additional contact as a maul has been created and there is no ball carrier.

Inter rater study tackle coding manual 5-A

Foul Play Laws 10.3 (e) and (h) define the following as dangerous tackles: x A player must not tackle an opponent early, late (tackler is not committed to the impact) or dangerously x A player must not tackle (or try to tackle) an opponent above the line of the shoulders. A tackle around the opponent’s neck or head is dangerous play. x A ‘stiff-arm tackle’ is dangerous play. A player makes a stiff-arm tackle when using a stiff-arm to strike an opponent. x Playing a player without the ball is dangerous play. x A player must not tackle an opponent whose feet are off the ground. x Tackling the jumper in the air. A player must not tackle nor tap, push or pull the foot or feet of an opponent jumping for the ball in a line-out or in open play.

These plays are known to place the ball carrier at an unacceptable risk of injury and are penalised. They should not be coded as tackles (IRB or otherwise), but their occurrence can be noted separately.

Coding Instructions In order to undertake the analysis, you will be given a DVD containing the video footage for the study. The tackle workbook is also on this DVD along with a copy of this manual. You are encouraged to watch a tackle through as many times as required, prior to coding it. You are also able to review footage slowly or frame by frame to make sure that you code the tackle correctly.

Viewing order You will find 24 video files in the video folder. We understand the time demands to code all of this video footage may exceed that which you can spare.

As a minimum for the study to be effective, we ask that you watch and code the pre-prepared footage in videos 1-10 first before completing the coding of fivemins1.mp4.

Upon completion of this we encourage you to code the pre-prepared footage in videos 11-20 followed by fivemins3.avi if the time demand is not too great. If you cannot code all of the footage given to you, we would ask that you at least count the number of tackle events you observe in passages of game play (fivemins3.avi and fivemins2.mp4) and note down the counter code at the time of the tackle. You can use the tackle macro to do this, simply enter the file name and counter code in the relevant fields for each tackle that you observe and click enter.

If at any stage you have any questions regarding the coding procedure or the study, or encounter problems with the video or the macro, please contact:

Sydney London Trevor Savage or Becky Cancea University of NSW Rugby Football Union (02) 9385 6547 (0) 1249 715298 [email protected] [email protected] 6-A IRB Tackle study

Using the macro’s in the workbook To use the tackle workbook you must have macro’s enabled. The macro will save all of the field values that you have selected to another sheet within the workbook for analysis. If you receive the following error message on opening the workbook:

then you need to adjust the security settings in Microsoft Excel. To do this, select ‘options’ from the tools menu and then click on the security tab. Click on the Macro security button on the bottom right hand corner of the dialogue box to display the security settings and adjust the level to medium. Now each time you open a work book that contains macro’s you will be asked if you want to disable them.

The analysis has been separated into two parts. An upper level analysis which is coloured yellow in the macro which must be completed for all tackle events. A second lower level of analyses contains criteria to examine specific tackle variables for the tackler and the ball carrier which may not always be possible to complete.

Inter rater study tackle coding manual 7-A

The upper level: Generic tackle descriptors The upper level contains 28 fields describing general information about the event, such as the location on the field, the phase of play before and after and the ground conditions (Figure 1). You need to complete each of these fields for every tackle event you code. The majority of the fields use combo boxes which list all of the options available to you. These items are predictive text, so upon typing the first few letters of the desired coding in the box matching text will be displayed. Alternatively you can click on the arrow on the right side of the box to display the complete field listing. Once the box contains the desired text, click on the ‘next’ item to move on.

Figure 1: The upper level analysis

You will note that some of the drop down menus and cells have been disabled. These fields do not need to be considered for the inter-rater study, but they will be included in either or both of UNSW’s or the RFU’s analyses.

Upon completing the coding of a tackle, you need to save the data that you have entered by clicking on the enter button. This will refresh the form and save all of the information to another sheet within the workbook.

8-A IRB Tackle study

The Upper level analysis is coloured yellow and contains the following fields:

Event type: Classify the type of event that you are seeing. There are four options to select from: x A Generic tackle with no obvious injury to either player x A Knockdown event where one or more players is in obvious discomfort and does not return tho their feet immediately x A Medical Aid sought event where one or more players seeks medical attention following the tackle event. This includes the magic water bottle x An event where one or more players leave the field as a direct result of the tackle

Ball Carriers Club and Opposition Club: Identify the club of the Ball carrier and their opponents. A list of clubs used in the video footage and a description of their jerseys is outlined below:

Barker Red and navy blue striped jersey. Navy blue shorts Cranbrook Red, white and black striped jersey. Navy blue shorts Eastwood Blue and white jersey, Blue shorts England White jersey and shorts with red panel under the sleeves Gordon Green, yellow and black striped jersey with green shorts Grammar Yellow and black striped jersey Ireland Green jersey and shorts with white panel under the sleeves London Irish Green London Wasps Yellow /black Parramatta Blue, navy blue and white striped jersey, blue shorts Riverview Blue and white striped jersey, blue shorts Scots Yellow jersey, navy shorts or yellow and navy striped jersey Shore Navy blue jersey with diagonal white stripes. Navy shorts Southern Districts Red, sky blue and white striped jersey Waverley Blue and yellow striped jersey, blue shorts or blue jersey with yellow V Unsure

Counter ID: During the two 10 minute passages of play you will see an eight digit counter code in the top right hand corner of the screen. Please note down the counter code at the start of the event. This is for indexing purposes and does not reflect when you thought the tackle event started. Please note that a counter code does not need to be recorded for the pre-cut footage.

Inter rater study tackle coding manual -A

Phase of play before: What was the phase of play immediately preceding the tackle event? Was it: x A Tackle (A contact event where an opponent attempted to stop the ball carrier) x A Scrum (A set piece where the forwards from both sides scrummage for possession of the ball) x A Ruck (A contest for the ball on the ground) x A Maul (A contest for the ball where all players are on their feet) x A Lineout (A contest for the ball x Open Play (A period of play without ball contest such as tackles or set pieces, eg a backline move or run) x A Kick in Open Play (A kick following open play defined above eg a chip-chase or kick ahead) x A Kick off/Restart x Unsure

Tackle Type: Using the definitions below, how would you define the method of the tackle event? x Active (Obvious leg drive and forward momentum) x Passive (No leg drive or assertive step into the tackle, after the initial impact the tackler uses their arms to latch onto ball carrier and goes with the impact) x Jersey (Tackler grabs the Ball carrier’s jersey to execute the tackle) x Ankle tap (Tackler trips the ball carrier with their hand) x Smother (Tackler lands with his body wrapped around the ball carrier) x Minimal contact (A reaction tackle used in response to an acute change of attacking direction, causing a tackler to flay an arm out in an unbalanced position, with no supporting body weight, in an attempt to stop the carrier)

Tackle complete/Is this an IRB Tackle: According to the IRB law was this a tackle (i.e. did the ball carrier go to ground) ?

Law 15.3 BROUGHT TO THE GROUND DEFINED (a) If the ball-carrier has one knee or both knees on the ground, that player has been ‘brought to ground’. (b) If the ball-carrier is sitting on the ground, or on top of another player on the ground the ball-carrier has been ‘brought to ground’. if no Why: If the event was not a tackle according to law 15, then what would you describe it as ? x A Missed Tackle (The ball carrier evades the tackle contact – completely) x A Break Tackle x Held up/Maul

10-A IRB Tackle study

Phase of play after: What was the phase of play immediately after the tackle event? (Using the definitions outlined in phase of play before), was it: A Tackle A Scrum A Ruck A Maul A Lineout Open Play A Kick in Open Play A Kick off/Restart A Try Unsure

Tackler Sequence: What was the role of the tackler in the tackle? One on one (The tackler who applies the primary resistive force) Simultaneous (A tackle event in which two tacklers make contact with the ball carrier ‘simultaneously’) Sequential (A tackle event where the ball carrier is already held and is tackled by another player) Unsure

Retains ball: Does the ball carrier retain the ball? Yes/No/Unsure

Number of tacklers: Enter the number of tacklers involved in the tackle event in the text box

Inter rater study tackle coding manual -A

Location information Field Half: Please identify which half the incident occurred in. Was it: The Ball Carriers Own half The Oppositions Half Or Are you Unsure

Field Corridor: (Figure 2) Identify which corridor on the field the tackle occurred in. Three corridors have been defined for the study, running length ways along the field from end line to end line. These are: x Right Flank (from the Ball carrier’s right side line to the line 15 metres in from the sideline) x Left Flank (from the Ball carrier’s left side line to the line 15 metres in from the sideline) x Mid Field the area in the middle of the field between the two 15 metre lines x Select unsure if you are unable to determine the corridor

Right Left Mid field Mid field flank flank

22

In goal

Figure 2: Corridors with respect to the ball Figure 3: Aisles carrier’s defensive half

12-A IRB Tackle study

Field Aisle: (figure 3) Identify which aisle on the field the tackle occurred in. Three aisles have been defined for the study, running across the field from sideline to sideline. These are: x Mid-field (The area from the halfway line to the 22 metre line) x 22 (the area from the 22 metre line to the try line) x In goal (the area from the try line to the end line) x Select unsure if you are unable to determine the field aisle

Impact Force: What was your impression of the impact force on the ball carrier for this tackle? x High x Low x Unsure

Referees decision: What was the referee’s decision as to the legality of the tackle? x Legal x Free Kick x Penalty – technical x Penalty – foul play x Sin bin x Sent off

Field and Match Conditions Ground Dry: Was the playing surface dry at the time of the tackle? (Yes/No/Unsure)

Raining: Was it raining at the time of the tackle? (Yes/No/Unsure)

Was the player attempting to score: Was the player attempting to ground the ball to score a try at the time of the tackle? (Yes/No/Unsure)

The remaining six fields contain variables to identify position, relative size differences and evasion amongst other things, for the ball carrier and tackler. These fields need to be completed for each tackle event coded, so they have been included at the upper level of analysis. If more than one tackler is involved you need to complete these fields for each tackler. The process for analysing tackles with more than one tackler will be outlined on page 15.

Position: For both the ball carrier and tackler. What is the jersey number of the player? Please enter ‘obscured’ if it cannot be seen

Inter rater study tackle coding manual -A

Evasion technique: Did the ball carrier try to evade the tackle before the impact? Is so what main method did they employ? x Side Step (Immediately prior to the point of impact between the tackler and the ball carrier, the carrier attempts to side step the oncoming tackler) x Swerve (Immediately prior to the point of impact between the tackler and the ball carrier, the carrier attempts to evade the oncoming tackler by arcing their running line) x Gassed (Immediately prior to the point of impact between the tackler and the ball carrier, the carrier attempts to evade the tackle by sprinting away from the oncoming tackler) x Duck (Immediately prior to the point of impact between the tackler and the ball carrier, the carrier attempts to duck below the oncoming tackler) x Dummy (Immediately prior to contact, the ball carrier shapes to pass the ball, stopping at arm extension, then retracting ball, continues onwards) x Show and Go (Immediately prior to contact the ball carrier shapes to pop pass by presenting the ball to a supporting player, then retracts the ball and continues onwards) x Kick (Immediately prior to the tackle, the ball carrier attempts to kick the ball out of hand(s)) x No Evasion (Immediately prior to the point of impact between the tackler and the ball carrier, the carrier makes no attempt to evade the oncoming tackler)

Ball Outcome: What happened to the ball outcome following the tackle event? x Passed before tackle event x Run through (Ball carrier runs through tackle, and continues breaking forward) x Offloaded from feet (Ball carrier is held in a tackle, but does not go to ground and passes the ball to a team mate) x Spilled (Loss of control of the ball, ball strip, knock on, drop ball) x Offloaded from ground (Includes place ball and present ball) x Mauled x Rucked x Other x Unsure

Relative Height: Indicate what you think the relative standing stature of the ball carrier is to the tackler. Is: x The ball carrier taller than the tackler x The ball carrier shorter than the tackler x The same size as the tackler x Unsure

14-A IRB Tackle study

Relative Mass: Indicate what you think the relative mass of the ball carrier is to the tackler. Is: x The ball carrier larger than the tackler x The ball carrier smaller than the tackler x The same size as the tackler x Unsure

Can this Tackle be coded further? Can additional information about the tackle event, such as body position, ball carrier or tackler speed and direction, be recorded? Yes or No

If the answer is no, click ENTER and move onto the next tackle event

Coding tackles with two or more players In the event of a tackle containing two or more tacklers you need to code the information at the lower level separately for each ball carrier and tackler pair as the direction of the tackle, ball carrier awareness and body position etc may be different for each tackler. You should complete the entire form, including the upper level analysis for the first tackler and, before clicking enter to save the coding make a note of the tackle number indicated at the top of the worksheet. Click on enter to save the coding and refresh the form. You will notice that the tackle number has now increased by one. Change the tackle number so that it corresponds with the number given to the first tackler, and then complete the fields in the ball carrier and tackler columns for the second tackler. Repeat this process for any additional tacklers active during this tackle event.

Inter rater study tackle coding manual -A

The lower level: Specific tackle event information The lower level contains 69 fields describing specific information about the event, such as awareness of opponents, speed, tackle direction, feet alignment and special criteria for falling (Figure 1). If you indicated that the tackle could be coded further in the previous section then you need to complete each of these fields. If your view of any specific aspect is obcured you should place unsure or unknown in the combo box. Once again, the majority of the fields use combo boxes which list the options available to you. These items are predictive text, so upon typing the first few letters of the desired coding in the box matching text will be displayed. Alternatively you can click on the arrow on the right side of the box to display the complete field listing. If what you’re seeing is not on the list, you can add it to the box for that tackle. Once the box contains the desired text, click on the ‘next’ item to move on.

16-A IRB Tackle study

Awarness, speed and body position:

Aware of the tackler: Is the Ball carrier aware of the tackler? Is the tackler within the Ball carrier’s field of view or has the ball carrier sighted the tackler at some stage? Yes/No/Unsure

Eyes on ball carrier: Did the tackler have their eyes on the ball carrier up to and during the initial tackle contact? Yes/No/Unsure

Was the ball carrier supported? Did the Ball carrier have support players that they could have passed/offloaded to? Yes/No/Unsure

Ball Carry Method: What was the ball carry method? x Two hands (Ball in two hands or passing with two hands) x Lead Arm (Ball carried by the arm on the impact side) x Following Arm (Ball carried by the arm on the side adjacent to the impact) x Unsure

Speed of Ball Carrier: What is your impression of the speed of the ball carrier? x Still/Stationary x Slow (i.e. jogging) x Fast (i.e. sprinting) x Unknown

Direction of travel: Please indicate the direction of travel of the players using a co-ordinate axis system based on the main direction of travel prior to impact. The axis are applied globally. x The x axis runs down the length of the field parallel to the sideline. Movement of Ball Carrier towards the opposition’s try line is positive. x The y axis runs across the field parallel with the try line. Movement towards the right sideline is positive y, towards the left sideline is negative y.

Therefore a value of (x, y) for the ball carrier indicates diagonal movement towards the try line. A value of (0, y) indicates the player is traversing across the field to the right. Finally a value of (–x, y) indicates the ball carrier is moving diagonally, right and back towards his try line,

Important Please Note: the coordinate axis system and direction (positive and negative) is the same for describing the ball carrier and tackler.

Inter rater study tackle coding manual 7-A

x

y

T1 T2

BC BC = (x,0); T1 = (-x,-y);

T2 = (0,y);

Figure 4: The rugby field, showing a co-ordinate axis system and the direction of travel for the ball carrier and two tacklers based on these axes

x x y y

Figure 5: An example of direction of travel evaluation using co-ordinate axes. In this situation, the ball carrier’s direction- of travel is (x, y) and the tacklers direction of travel is (-x, y).

18-A IRB Tackle study

Body orientation of Ball Carrier Please indicate the body orientation of the ball carrier with reference to the direction of travel. Is it: x Front (the ball carrier is facing the direction of travel, ie. He is running forwards) x Behind (the ball carrier has their back to the direction of travel, ie. He is running backwards) x Right Side (the ball carrier is side on to the direction of travel) x Left Side (the ball carrier is side on to the direction of travel) x Unsure

Leg drive, posture and footwork Back Straight: Was the Ball carrier’s back straight at the time of impact? Yes/No/Unsure

Shoulders Rounded: Were the Ball carrier’s shoulders rounded (was the player squeezing the ball?) at the time of the impact? Yes/No/Unsure

Feet alignment: This field is trying to ascertain whether the player’s feet were positioned to generate force or to provide a good base for a reaction force of the tackle impact. Are the players feet: x Splayed (One foot in front of the other with reference to the opponent) x Parallel (Feet side by side) x Unsure

Figure 6: Feet position in tackle. The Tacklers feet are aligned parallel; the Ball carriers feet are splayed.

Inter rater study tackle coding manual -A

Stance width/length: Please indicate the approximate stance width/length of the player. Is it: x Feet more than shoulder width x Feet less than shoulder width x Only one, or no feet contact x On knees x Unsure

Steps into tackle: Does the player make take a step forward leading into the tackle event? Yes/No/Unsure

Feet adjacent/Steps to base: Does the Ball carrier get a leading foot position close to the tacklers leading foot? Yes/No/Unsure

Knees bent: Are the ball carrier’s knees bent when entering the tackle? Yes/No/Unsure

Feet Preparation: x Small Steps x Wide Steps x No Movement x Unsure

Extends lower body: Yes/No/Unsure

Tackle Description:

Tackle direction: Please indicate from which direction the tackle is coming from. This is regardless of the Ball carrier’s running direction. Is it: x Front (from in front of the ball carrier) x Behind (from behind) x Right Side x Left Side x None x Unsure Front

Left Right

Side Side

Rear

Figure 7: Direction of tackle (with thanks to Ken Quarrie, NZRU) 20-A IRB Tackle study

Arms Grapple: Does the tackler wrap their arms around and hold on to the ball carrier? Yes/No/Unsure

Ball Carrier lifted by tackler: Was the ball carrier lifted from ground contact by a tackler? Yes/No/Unsure

Region Struck: Head Chest

Neck Shoulder Chest Back Abdomen Abdomen

Shoulder Upper Back Upper limb Hip Hips Thigh Thigh Knee Knee Lower leg Lower Leg

Head position in tackle: What is the tacklers head position in the tackle event? Is it: x Above (above the ball carrier, eg smother tackle) x Behind (at the back of the ball carrier) x In front (sandwiched between the bodies of the ball carrier and tackler or tackling with head on the falling side of the ball carrier) x Beside (Either side of the ball carrier) x Unsure

Head and neck flexion: What is the main position of the head and neck at impact? x Head up (Head/neck in a neutral or extended position relative to the trunk) x Chin on chest (Head/neck in a flexed position) x Unsure

Body Posture: What is your impression of the Ball carrier’s body posture? x Low (small compact body shape) x High (long/tall body shape, no abdominal or lower limb flexion) x Falling/Diving x Unsure

Lower body position than Ball Carrier? Did the tackler adopt a lower body position prior to the tackle than the ball carrier? Yes/No/Unsure Inter rater study tackle coding manual -A

Small steps in contact: Does the Ball carrier take small steps in contact? Yes/No/Unsure

Direction after impact: Please indicate the direction of travel of the ball carrier After/in the tackle using a co-ordinate axis system. The axes are applied the same as for direction of travel: x The x axis runs down the length of the field parallel with the sideline. Movement towards the opposition’s try line is positive. x The y axis runs across the field parallel with the try line. Movement towards the left sideline is positive y, towards the right sideline is negative y.

x

y

T2 T1

BC Post tackle (-x,0)

Figure 7: The rugby field, showing a co-ordinate axis system and the direction of the tackle unit (ball carrier, and tacklers) after impact.

22-A IRB Tackle study

Tackle Bust method: Does the ball carrier attempt to break the tackle contact by employing: x Shoulder bump (At point of impact between the tackler and the ball carrier, the carrier attempts to turn their shoulder into the oncoming tackler and bump them) x Ball bump (At point of impact between the tackler and the ball carrier, Ball Carrier wraps ball to chest and attempts to bump the tackler using the ball for impact) x Hit and Spin (At the point of impact between the tackler and the ball carrier, Ball Carrier spins off the tackler in an attempt to break the tacklers grasp) x Hand Off (Physical push away or down) x Arm Fend (use of arm to fend, or act as a buffer pre contact) x Hip Bump (At the point of impact between the tackler and the ball carrier, Ball Carrier attempts to bump the oncoming tackler with their hip / thigh area) x High Knees (At the point of impact between the tackler and the ball carrier, the carrier attempts to evade the oncoming tackler by accentuating a high knee lift in their run stride) x No Evasion (At the point of impact between the tackler and the ball carrier, the carrier makes no attempt to evade the oncoming tackler)

Secondary impact with another tackler? Did the tackler collide unintentionally with another tackler? Yes/No/Unsure

Inter rater study tackle coding manual -A

Ground Impact

Was there a ground impact for the Ball Carrier? Yes/No/Unsure

Striking object: What was the striking object during the secondary impact? x Ground x Goal Post x Fixed Object x Spectator x Referee x Other

Region Struck: What was the main region struck during the secondary impact?

Head Chest Neck Shoulder Chest Back Abdomen Abdomen

Shoulder Upper Back Upper limb Hip Hips Thigh Thigh Knee Knee Lower leg Lower Leg

Final position of tackle: Upon coming to rest what was the final position of the ball carrier and tackler on the ground? x Tackler on top x Ball carrier on top x Fell separately x Both on feet x Other x Unsure

Region loaded: Which body region absorbed most of the ground impact? (eg the elbow may make contact with the ground, but the shoulder joint is placed under the most load) x Head/Neck x Upper limb/Shoulder x Lower Limb x Trunk (Thorax, abdomen & pelvis) x Unsure x None

24-A IRB Tackle study

Injury associated with ground impact? Yes/No/Unsure

Range of motion exceeded: Was the affected joint placed in hyper-extension? Yes/No/Unsure

Tackler contribute to the magnitude of load? Did the tackler contribute to the load experienced by the ball carrier?

Limb motion retarded: Was the limb associated with the loaded region prevented from moving freely? (eg, tackler laying on a Ball Carrier’s foot or ground contact forcing joint into extreme range) Yes/No/Unsure

Loading pattern of main region affected: How was the force applied to the body/region loaded during the secondary impact? x Stretching of joint or limb x Impact (eg. direct blow) x Crush (eg. Player crushed between ground and tackler) x None x Unsure

Specific factors: Were any of the following factors observed? x Fall onto Outstretched Limb x Fall onto head/neck x Fall onto thorax/shoulder x Fall onto back/buttocks x Foot/lower limb locked and upper body twisting x Lifted & turned (spear tackle) x None/Other

Falling position: What was the falling body posture of the player? x Vertical/long/unrelaxed x Small x Unsure

Falling: In falling to the ground, was the ball carrier able to control the ball to maintain possession and limit the risk of injury? x Control Ball and prevent injury x Control Ball, risk of injury x Prevent injury, lose possession x Unsure

Inter rater study tackle coding manual -A

Summary of Instructions 1. Coding method a. Watch the video as many times as necessary b. As a minimum, please code videos 1-10 followed by the passage of play in fivemins1.mp4 c. If time permits, please code videos 11-20 d. If time permits, please code the passage of play in fivemins3.avi e. If you do not have time for c. or d. above, please identify tackle events in fivemins3.avi and code the counter code using the tackle workbook

2. Upper level a. Complete all fields for every tackle event being coded b. Enter unsure in any fields where the event cannot be discerned from the video c. For game passage video, include the counter code from the video footage in the ‘counter ID’ field d. Include the number of tacklers. If more than one, make a note of the tackle identification number in the top left hand corner of the worksheet

3. Lower Level a. Complete this section if the specifics of the tackle event (such as tackle direction, region struck, and posture) are not obscured. b. Only code the ‘falling’ fields when there is a ground impact/contact

4. Pairs of ball carrier-tackler a. Tackles need to be considered in ball carrier-tackler pairs for each tackler in the same event as the variables (direction, region struck) will change b. For tackles where there is more than one tackler, complete a lower level analysis for all ball carrier and tackler pairs by: - Making note of the initial tackle number before saving - Save the record and then change the tackle ID to correspond with the preceding analysis - Complete a new lower level analysis for the second tackler and ball carrier, even if the impact has similar characteristics to other tacklers coded

Please note that the user interface was prepared for the inter rater study and will be revised for the full study.

The chief investigators are interested in your feedback for the study. Please complete the short questionnaire on the coder information sheet in the tackle workbook. Your comments will be used to refine the study.

The researchers at UNSW and the RFU thankyou for your assistance with this study.

26-A IRB Tackle study APPENDIX B

CODING WORKBOOK FOR THE FIRST INTER-RATER

RELIABILITY STUDY

249

Graphical user interface from IRR1 coding work book for the Upper level analysis

Graphical user interface from IRR1 coding work book for the lower level analysis

Graphical user interface from IRR1 coding work book for the ground contact analysis

251

252 APPENDIX C

WORKED EXAMPLE OF PERCENTAGE AGREEMENT

253

Data from IRR1

Equation is presented on page 104

*Sum of the product for each column by N (ij×ij + ij×ij...) –column total

†Sum of the product for each column and the number of raters per target

§Mean Po is calculated by dividing a by b

254 Categories (j=3) Tacklers eyes on Ball carrier Total Target (i) (1.) (2.) (3.) (sum (N=30) Yes No Unsure 1,…k) 1.0 9009 2.0 7209 3.0 8008 4.0 8109 5.0 9009 6.0 9009 7.0 8109 9.0 8008 10.0 8008 11.0 7007 11.1 6006 12.0 5005 13.0 6017 13.1 4105 14.0 7007 17.0 3003 18.0 6006 18.1 6006 19.0 5005 20.0 4004 22.0 5005 23.0 4004 23.1 6107 25.0 4004 26.0 6006 27.0 3003 28.0 3003 28.1 6006 29.0 3003 30.0 7007 Total 180 6 1 187 (Sum i for j) Sum of 1,008 1,006 2 0 product* (a) Sum of 1,100 1,052 42 6 product† (b) Mean Po 0.96 0.05 0.00 0.92 §

255

APPENDIX D

CODING MANUAL,INTER-RATER RELIABILITY

TESTING,PHASE 2

257

IRB Tackle study

Second Inter Rater Reliability Study (IRR2)

Coding Manual

Trevor Savage

September 2007

D-i IRB tackle study: IRR2 Tackle coding Manual

Table of Contents ANALYSIS BACKGROUND AND AIMS ...... D-1 THE TACKLE PROTOCOL ...... D-2 THE ANALYSIS PROCESS ...... D-2 TACKLE DEFINITION ...... D-4

THE UPPER LEVEL ...... D-6 Using Snapper ...... D-7 Creating a Project ...... D-7 Adding video files ...... D-7 Logging events ...... D-7 Upper Level analysis fields: ...... D-8 Generic tackle descriptors ...... D-8 Game time: ...... D-8 Event type: ...... D-8 Tackle Type: ...... D-9 Tackle event reference time (T0) ...... D-9 Number of tacklers: ...... D-10 Is this an IRB Tackle/is the tackle complete: ...... D-10 If the tackle event was not complete: ...... D-10 Team, Field Location, Field Condition and Weather Information ...... D-11 Ball Carrier’s Team and Tackler’s Team: ...... D-11 Level ID: ...... D-11 Field Half: ...... D-11 Field Corridor: ...... D-12 Field Aisle: ...... D-13 Winning: ...... D-13 Raining: ...... D-13 Ground Dry: ...... D-13 Match Conditions ...... D-14 Phase of play before: ...... D-14 Phase of play after: ...... D-15 Impact Force: ...... D-15 Retains ball: ...... D-15 Was the player attempting to score? ...... D-15 Can this Tackle be coded further? ...... D-15

THE LOWER LEVEL ...... D-16 Using the Tackle Database ...... D-17 Impact sequence and the lower level data entry page ...... D-17 Viewing projects in Snapper ...... D-18 General Information with no specific reference time ...... D-19 Jersey Number/Position: ...... D-19 Injury to Ball Carrier: ...... D-19 Was there an injury to the ball carrier? ...... D-19 Evasion technique: ...... D-19 Relative Height: ...... D-19 Relative Mass: ...... D-19 Fields to be analysed at T0 ...... D-20 Back Straight: ...... D-20 Shoulders Rounded: ...... D-20 Feet adjacent/Steps to base: ...... D-20 Knees straight: ...... D-20 Tackle direction: ...... D-21 Body Region struck on ball carrier or tackler: ...... D-22 Head and neck position: ...... D-25 Stance height: ...... D-25 Head position in tackle ...... D-25 Fields to be analysed 5 frames or more before the tackle impact (T<-5) ...... D-26 Steps into tackle:...... D-26 Was the ball carrier supported? ...... D-26 IRB Tackle Study D-ii

Aware of the tackler: ...... D-26 Fields to be analysed over a specified period from 10 frames before the tackle impact (T-10 to T0 or T5) . D-26 Speed of Ball Carrier/Tackler: ...... D-26 Direction of travel: ...... D-26 Body orientation of Ball Carrier: ...... D-28 Small steps in contact: ...... D-28 Fields to be analysed over a specified period from 5 frames before the tackle impact (T-5 to T0 or T5) .... D-29 Ball Carry Method: ...... D-29 Tackle Bust method: ...... D-29 Feet alignment: ...... D-30 Stance width/length: ...... D-30 Lower body position than Ball Carrier? ...... D-30 Fields to be analysed after the tackle impact leading up to ground contact ...... D-31 Ball Carrier lifted by tackler: ...... D-31 Direction after impact: ...... D-31 Arms Grapple: ...... D-32 Secondary impact with another tackler? ...... D-32 Was there a ground impact for the Ball Carrier/tackler? ...... D-32

GROUND CONTACT ...... D-33 Striking object: ...... D-34 Falling body posture: ...... D-34 Final position of tackle: ...... D-34 Injury associated with ground impact? ...... D-34 Specific factors: ...... D-35

SUMMARY OF TIMING OF ANALYSIS...... D-36 Variables evaluated at T0 ...... D-36 Variables evaluated within -5 frames of T0 ...... D-36 Variables evaluated within -10 frames of T0 ...... D-36 Variables evaluated prior to -10 frames of T0 ...... D-36 Variables evaluated after T0 (note specific reference time) ...... D-37 Fields with no specific analysis time ...... D-38

STUDY CHECKLIST...... D-40

Table of Figures Figure 1: An Outline Of The Coding Process ...... D-3 Figure 2: Field Corridors With Respect To The Ball Carrier’s Defensive Half...... D-12 Figure 3: Field Aisles With Respect To The Ball Carrier’s Defensive Half...... D-13 Figure 4: The Lower Level Data Entry Form’s Paired Analysis Of Ball Carrier And Tackler Variables. D-18 Figure 5: Direction Of Tackle (With Thanks To Ken Quarrie, Nzru) ...... D-21 Figure 6: Body Chart Showing The Definitions Of Body Region For The Body Region Struck During Tackle Contact...... D-24 Figure 7: Head Position Of The Tackler During The Tackle Contact Showing A Head Position Above, Behind, In Front And Beside...... D-25 Figure 8: The Rugby Field, Showing A Co-Ordinate Axis System And The Direction Of Travel For The Ball Carrier And Two Tacklers Based On These Axes...... D-27 Figure 9: An Example Of Direction Of Travel Evaluation Using Co-Ordinate Axes. In This Situation, The Ball Carrier’s Direction Of Travel Is (X, Y) And The Tackler’s Direction Of Travel Is (X, -Y). . D- 27 Figure 10: Feet Position In Tackle. The Tackler’s Feet Are Aligned Parallel; The Ball Carrier’s Feet Are Splayed...... D-30 Figure 11: The Rugby Field, Showing A Co-Ordinate Axis System And The Direction Of The Tackle Unit (Ball Carrier, And Tacklers) After Impact...... D-31

D-iii IRR2 Tackle Coding Manual Analysis background and aims Rugby Union is a contact team sport which evolved from soccer in the 19th century. It is characterised by skills producing high-energy collisions such as the tackle, maul, scrum, and the ruck. These skills have potential injury risks which are inherent to collisions and impact. Serious injuries to the knee and shoulder can occur in the tackle, and there is a risk of catastrophic spinal injury in the scrum. To remove the skills from the game would change its nature drastically. When performed with the proper technique and in the spirit of fair play, the injury risk can be reduced to acceptable levels.

The large proportion of injury research conducted in rugby has focused on the risk and causation of catastrophic spinal injuries (CSI) in the scrum. The results lead to changes in the laws of the game to reduce the risk of injury. The alterations to the laws were introduced at the youth (U19) level of the game and effectively de-power the scrum, encouraging the development of the skills and a gradual increase in the load so that players are able to participate safely by the time that they reach the open age group. The effectiveness of protective equipment in preventing rugby injures (such as mouth guards and headgear) has also been examined. In recent times, the focus of injury research has shifted to identification and monitoring, with the unions in Australia, England and New Zealand conducting ongoing injury surveillance studies to assess changes in rates of injury. In all of these studies, the tackle has been identified as the event with the largest injury risk, accounting for between 40 and 50% of all rugby injuries. While both the tackler/s and ball carrier can be injured in the tackle, this research has indicated that the ball carrier is twice as likely to be injured in the tackle situation as the tackler.

Considering the high frequency of tackles per game (approximately 200), it is not surprising that it is a skill associated with a high proportion of injuries. The body contact involved with the tackle impact and the fall that may eventuate, present risks of a serious joint injury, fracture or concussion. The International Rugby Board (IRB) has supported the development of an analysis protocol for the tackle to examine injury risks. The protocol has been drafted by the Biomechanics research group at the University of New South Wales (UNSW) in collaboration with the Rugby Football Union (RFU). The protocol aims to identify the characteristics of the tackle event (skill and technique) that are associated with injury risks. It will be used in a broader study of tackle events to:

1. Investigate the aetiology of tackle related injuries 2. Investigate the specific characteristics of tackle skills and techniques related to injury causation 3. Assess the injury risks (frequency and consequences) associated with specific tackle skills

You are participating in a study to test the reliability of the protocol between observers. i.e. Do two people identify the same things when they view an event based on the definitions provided in this protocol?

IRR2 Tackle Coding Manual D-1 The tackle protocol The tackle protocol is the result of collaboration between two research groups from UNSW and the RFU. Each research group developed criteria independently with the assistance of coaching and officiating personnel, before combining the two methods to establish a protocol to categorise the variables involved in tackle technique. The development of a common protocol provides the benefits of establishing a standard method of analysis for future research and allowing comparison of current studies. By applying the protocol to a number of tackle events, including those that lead to injury and those that do not, factors and technique correlating with injury risk can be identified. This information could then be used in a subsequent study to design a training program that encourages the development and adoption of safe and effective tackle skills appropriate for age and competition level. The protocol contains 96 fields which have been separated into two levels of analysis; an upper level consisting of generic tackle descriptors and a lower level describing specific technique attributes of the players involved.

The Analysis Process Two five minute Video clips taken from one colt’s game have been selected for the study. You are asked to review the video footage and to identify and code any events which you identify as tackles according to the definitions provided in this manual. To evaluate tackle fields at the upper level of the study you will use SnapperTM. Snapper is a video analysis program allowing users to navigate the video footage and to catalogue the events. It will record the information entered via the graphical interface, linking it to the event footage and allowing for easy navigation through game events. Lower level codings will be recorded to a Microsoft Access database. When coding the lower level, you should navigate through the footage of the event using the Snapper ‘Event list’ created in Snapper while coding the details to the Access database. The steps involved in the coding process are outlined in Figure 1. For more information on Snapper and the upper level please see page D-8. Please see page D-17 for more information about the lower level and using the Access database.

It is important to remember that you are assisting with a scientific study and that the results are as relevant as possible. Therefore:

If at any time an event or field can not be evaluated with certainty, it should not be coded. It is important that you only code what you see, not what you think or assume may have happened, even if this is based on playing experience.

If you have any additional thoughts or comments about a tackle event, these should be written in the additional notes field on the tackle pair form.

You may complete the analysis in any manner you wish, either by completing all details for a tackle as you identify it (upper and lower level) or by completing the coding in multiple passes where all tackles are first identified in Snapper, then the upper level coding is completed followed by the lower level coding.

D-2 IRB Tackle Study

Does the contact event No The event can’t meet the studies be coded definition for a tackle?

Yes Yes Is the Tackle Analysis complete type obscured? The tackle should be counted only No No Can the event be coded accurately?

Yes Upper level, see page D-8 The event can be coded at the upper level

Can additional No information Analysis complete about the tackle Do not code the lower level be gained?

Yes

The lower level should Lower level, see page D-17 be coded

No Was there a Analysis Complete ground impact

Yes

No Can the contact be coded accurately?

Lower level, see page Error! Bookmark not defined. Code the ground impact

Coding Complete

Figure 1: An outline of the coding process

IRR2 Tackle Coding Manual D-3 Tackle definition The first step of the analysis is to identify tackle events from other collisions. There are many contact plays in rugby union which an observer may classify as tackles. We need to ensure that all relevant events are coded, while ensuring that the data obtained remains relevant and useful.

According to the IRB rule book, the definition of a tackle is as follows:

Law 15 - The Tackle A tackle occurs when the ball-carrier is held by one or more opponents and is brought to ground. A ball-carrier who is not held is not a tackled player and a tackle has not taken place. Opposition players who hold the ball-carrier and bring that player to ground, and who also go to ground, are known as tacklers. Opposition players who hold the ball-carrier and do not go to ground are not tacklers.

Thus, under the IRB definition if the ball carrier does not go to ground or if the player breaks through a ‘tackle contact’ then a tackle has not occurred. This law serves as a reference base for identification of the phase’s of play immediately following a complete ‘tackle’ such as rucks and mauls rather than describing or defining a tackle event. Most observers of the game would call any attempt to stop a player with the ball ‘a tackle’. Therefore for tackle analysis, the definition set out in the Oxford English dictionary is more relevant to the study:

5. (a) In Rugby, to seize and stop (an opponent) when in possession of the ball.

Because injuries can occur in tackle events which do not go to ground (as per law 15), all incidents where the opponent (and thus ‘tackler’) is attempting to stop the ball carrier should be considered for analysis. This may include attempted tackles in which the ball carrier breaks through or evades the tackle contact completely (missed tackles), or ‘tackles’ in which the ball carrier is held up, amongst many other situations. If in the opinion of the observer the opponent is attempting or has the intention to stop an opponent in possession of the ball then it should be coded.

D-4 IRB Tackle Study

There are some exceptions which would generally not be included in an analysis of standard tackle technique. These include:

Charge down events Events where an opponent was attempting to play at the ball rather than tackle the ball carrier. These will generally occur when the ball carrier has disposed of possession through kicking or passing and may include attempts to intercept a pass or charge down a kick.

The Maul Law 15.2 defines a maul as a situation when a tackle cannot take place (When the ball- carrier is held by one opponent and a team-mate binds on to that ball-carrier, a maul has been formed and a tackle cannot take place). In this case, the first phase in which the ball carrier is stopped by one or more opponents could be analysed, but not any additional contact as a maul has been created and there is no ball carrier.

Foul Play Law 10.3 (e) - Dangerous tackling.

x A player must not tackle an opponent early, late (tackler is not committed to the impact) or dangerously. x A player must not tackle (or try to tackle) an opponent above the line of the shoulders. A tackle around the opponent’s neck or head is dangerous play. x A ‘stiff-arm tackle’ is dangerous play. A player makes a stiff-arm tackle when using a stiff-arm to strike an opponent. x Playing a player without the ball is dangerous play. x A player must not tackle an opponent whose feet are off the ground. x Tackling the jumper in the air. A player must not tackle nor tap, push or pull the foot or feet of an opponent jumping for the ball in a line-out or in open play. x Dangerous charging. A player must not charge or knock down an opponent carrying the ball without trying to grasp that player.

These plays are known to place the ball carrier at an unacceptable risk of injury and have been outlawed. These tackles could be analysed as part of a case study examining the specific risks involved with these events.

If the contact event falls within the boundaries of our definition then we can proceed to the upper level.

IRR2 Tackle Coding Manual D-5

THE UPPER LEVEL

Using Snapper The first pass analysis to identify tackles, rucks, mauls, scrums and line outs is to be performed with Snapper, a PC based observational analysis program. Snapper records user defined events in selected footage through a graphical user interface (GUI). You will observe and navigate through the video footage using Snapper. Each separate Snapper analysis of video footage is known as a project, and common projects are arranged into groups. For IRR2 the group will be ‘IRR coding’ and the project file will be your name.

Creating a Project You do not need to create a project file as this has been created for you. All project files are located on biomech-15. Should you need to browse for these files the exact location is: C:\IRB Tackle Study\Groups\IRR coding

Adding video files The video files have already been added to your project. However, if an error occurs, you can add video files to a project by selecting project; video files from the menu bar. Click on the ‘add’ button on the dialogue box which opens and then select the video files to be used from the local hard drive.

Logging events Once the video is playing you need to click the buttons to record the occurrence of play that you observe. All passages of play will be recorded to evaluate the frequency of both the play and resulting injuries. Events to be identified in Snapper are: x Line out x Maul x Ruck x Scrum x Backline move (when the ball has passed through two pairs of hands or travelled 10m or more)

Events identified in Snapper which require additional information to be entered within the Access Database: x Tackle (timing varies for tackle type, see page D-9).

To Log these events to Snapper, open the event logging window by clicking on the coach’s clipboard on the tool bar or selecting it from the Events menu. Select the event that you want to log from the event logging interface and click on the green tick which is found at the bottom of this interface. To code tackle events at the upper level within the Access database, open the form F_tackles by clicking on the “add upper level coding” button on the switchboard. One record needs to be completed for each form. Use the record navigation buttons at the bottom of the form to locate the next blank tackle record for data entry. Most of the information on the form is selected from drop down menus or checkboxes. Game time will need to be entered manually. It is very important that you identify the correct time for the tackle in HH:MM:SS.ff format as other aspects of the protocol rely on this time for reference. Please refer to game time item on page D-8 and to the tackle event reference time item on page D-9.

IRR2 Tackle Coding Manual D-7 When coding, remember:

If at any time an event or field can not be evaluated with certainty, it should not be coded. It is important that you only code what you see, not what you think or assume may have happened, even if this is based on playing experience.

Upper Level analysis fields: Generic tackle descriptors The upper level contains 32 fields describing general information about the event, such as the location on the field, the phases of play occurring before and after the tackle and the ground conditions.

The second step of the coding process is to determine the event type. This will determine whether further analysis needs to be performed.

Game time: This is the counter code corresponding to T0 (Tackle event reference time; see the item on page D-9). The counter code is displayed in the video window in Snapper. It needs to be entered to the database in HH:MM:SS.ff format.

Event type: The event being recorded. There are five options to select from: 1. A general tackle event which does not result in an injury or obvious discomfort to either player. 2. A Knockdown event where one or more players appear to be in obvious discomfort and remain on the ground for more than 5 seconds. 3. A Medical Aid sought event where one or more players seeks medical attention following the tackle event. 4. An event where one or more players leave the field as a direct result of the tackle. 5. An event which is a tackle event but which the majority of the detail if fully obscured, preventing it from being coded meaningfully. A fully obscured event is counted as a tackle, but is not coded further at the lower level. Coding for all fields at the upper level still needs to be completed.

D-8 IRB Tackle Study

Tackle Type: The general technique of the tackle event using the definitions below. 1. Shoulder – A tackle in which the tackler’s shoulder is the first point of contact. A shoulder tackle could be: a. Active (Obvious hip and knee extension to create leg drive and forward momentum) Or b. Passive (No leg drive or assertive step into the tackle, after the initial impact the tackler latches onto the ball carrier using their arms and pulls the player to the ground) 2. Jersey – The tackler holds the ball carrier’s jersey to execute the tackle 3. Ankle tap – Tackler trips the ball carrier with their hand 4. Smother - Tackler engages the ball carrier with his arms wrapped around the ball carrier, trapping the ball 5. Arm short/long - A reaction tackle used in response to an acute change of attacking direction, causing a tackler to flay an arm out in an unbalanced position, with no supporting body weight, in an attempt to stop the carrier 6. Obscured – The tackle type can not be evaluated with certainty

The tackle type is especially important to the analysis as each tackle type has a specific reference point from which all other variables within the process should be evaluated. The tackle event reference time (T0) is explained below.

a) Tackle event reference time (T0)

The first contact of a body segment relevant to Tackle Type (see definitions in item below). T0 provides a temporal reference point for the viewer to inspect footage for the presence of variables for other fields in the analysis.

T0 should be evaluated as follows:

For a shoulder tackle, T0 occurs at first impact of the tackler’s shoulder with the ball carrier.

For an ankle tap, T0 occurs at first impact of the tackler’s arm with the ball carrier’s lower limb.

For a jersey tackle, T0 occurs when the tackler visibly grips in a bunch or hooked hand part of the ball carriers jersey.

For a smother tackle, T0 occurs at first impact of the tackler’s torso with the ball carrier.

For an arm tackle, T0 occurs at first impact of the tacklers arm with the ball carrier. This will be recorded using the Counter ID.

IRR2 Tackle Coding Manual D-9 Number of tacklers: The number of tacklers involved in the tackle event. (NB defensive players tackling the ball carrier whilst still held by tackler are participating in the same tackle event).

Players pushing the ball carrier or not attempting to stop the ball carrier are not participating in the tackle and should not be coded. Their involvement can be noted in the additional notes for the upper level.

Impact Sequence: Tackler interaction with the ball carrier (defined relative to first T0) 1. One on one (Only one tackler throughout the tackle event) 2. Simultaneous (A tackle event in which two tacklers make contact with the ball carrier ‘simultaneously’ i.e. within 5 frames after T0) 3. Sequential (A tackle event where the ball carrier is already held and is tackled by another player more than 5 frames after T0. The primary tackler should still be in contact with the ball carrier) 4. Unsure

Is this an IRB Tackle/is the tackle complete: The tackle fulfilled the requirements of law 15 (i.e. the ball carrier went to ground. For a definition of brought to ground see IRB law 15.3 below)

Law 15.3 - BROUGHT TO THE GROUND DEFINED (a) If the ball-carrier has one knee or both knees on the ground, that player has been ‘brought to ground’. (b) If the ball-carrier is sitting on the ground, or on top of another player on the ground the ball-carrier has been ‘brought to ground’.

If the tackle event was not complete: What occurred which prevented the event becoming a tackle according to law 15? 1. Missed Tackle (the ball carrier evades the attempted tackler’s contact completely) 2. Break Tackle (there is contact between the ball carrier and an opponent, but the ball carrier is not held and does not go to ground) 3. Held up/Maul (The ball carrier is held up on their feet by a tackler/s) 4. Offload from feet before ground contact (the ball carrier passes the ball during a tackle contact but before ground contact) 5. Unknown

D-10 IRB Tackle Study

Team, Field Location, Field Condition and Weather Information

Ball Carrier’s Team and Tackler’s Team: Identify the team of both the Ball carrier and the tackler. The clubs participating in the footage are Gordon (green, yellow and black stripes) and Parramatta (Dark blue with sky blue stripes).

Level ID: What is the level of the teams playing in the game? 1. Elite 2. Sydney Premiership 3. Country 4. Colts 5. Schoolboy Opens 6. Schoolboy U15

Field Half: The field half that the tackle occurred in: 1. Own; The Ball Carrier’s defensive half 2. Oppositions; The Ball Carrier’s attacking half 3. Or Unsure

IRR2 Tackle Coding Manual D-11 Field Corridor: The corridor on the field that the tackle occurred in. Three corridors have been defined for analysis, running length ways along the field from end line to end line (Figure 2). These are: 1. Mid Field (the area in the middle of the field between the two 15 metre lines) 2. Left Flank (from the Ball carrier’s left side line to the line 15 metres in from the sideline) 3. Right Flank (from the Ball carrier’s right side line to the line 15 metres in from the sideline) 4. Select ‘unsure’ if you are unable to determine the corridor

Figure 2: Field corridors with respect to the ball carrier’s defensive half

D-12 IRB Tackle Study

Field Aisle: The aisle on the field which the tackle occurred in. Three aisles have been defined for analysis, running across the field from sideline to sideline (Figure 3). These are: 1. Mid-field (The area from the halfway line to the 22 metre line) 2. 22 (the area from the 22 metre line to the try line) 3. In goal (the area from the try line to the dead ball line) 4. Select unsure if you are unable to determine the field aisle

Right Left Mid field flank flank

Figure 3: Field aisles with respect to the ball carrier’s defensive half.

Winning: At the time of the tackle, was the ball carriers team winning the game? (did they have more points than the opposition?) 1. Yes 2. No 3. Unsure

Raining: It was visibly raining at the time of the tackle 1. Yes 2. No 3. Unsure

Ground Dry: The playing surface was visibly dry at the time of the tackle 1. Yes 2. No 3. Unsure

IRR2 Tackle Coding Manual D-13 Match Conditions

Phase of play before: The phase of play immediately preceding the tackle event, selected from the list below: 1. A Tackle - A contact event where an opponent attempted to stop the ball carrier 2. A Scrum - A set piece where the forwards from both sides scrummage for possession of the ball (See IRB law 20). 3. A Ruck - A contest for the ball on the ground involving at least 3 players (one player from each team and the ball carrier - See IRB law 16). 4. A Maul - A contest for the ball where all players are on their feet involving at least 3 players (one player from each team and the ball carrier - See IRB law 17). 5. A Lineout - A restart event where the ball is thrown in from the sideline after the ball lands outside of the field of play (See IRB law 19). 6. A Backline move - A period of play without ball contest where: a. The ball passes through at least two Ball carriers’ hands or b. A ball carrier covers a distance of at least approximately 10 metres 7. A Kick in General Play – Any kick which is not a restart, eg. chip and chase or kick ahead. 8. A Kick off/Restart (including penalty and conversion attempts) 9. Scrappy or Open play – A period of play where possession of the ball is contested (i.e. neither team holds possession of the ball), but there is no structured phase, such as a ruck, maul or scrum. 10. Unsure

Where the phase of play prior to the tackle event occurs off camera or is obscured then it should be listed as ‘unsure’.

D-14 IRB Tackle Study

Phase of play after: The phase of play immediately after the tackle event? (Using the definitions outlined in phase of play before on page D-14) selected from the list below: 1. A Tackle 2. A Scrum 3. A Ruck 4. A Maul 5. A Lineout 6. Backline move 7. A Kick in general play 8. A Kick off/Restart 9. Scrappy or open play 10. A Try 11. Unsure

Impact Force: The viewer’s/analyst’s impression of the impact force on the ball carrier for this tackle: 1. High 2. Low 3. Unsure

Retains ball: The ball carrier’s team retains possession of the ball in the phase of play following the tackle: 1. Yes 2. No

Was the player attempting to score? The player was attempting to ground the ball to score a try at the time of the tackle: 1. Yes 2. No

Can this Tackle be coded further? Can additional information about the tackle event, such as body position, ball carrier or tackler speed and direction, be recorded? 1. Yes 2. No

If the tackle cannot be coded further then it should be identified as ‘fully obscured’ within the event type field (page 8).

IRR2 Tackle Coding Manual D-15

THE LOWER LEVEL

The lower level contains 69 fields describing specific information about the event, such as awareness of opponents, speed, tackle direction, feet alignment and special criteria for the analysis of the fall.

The lower level should only be completed if it is possible to gain additional information, especially with regards to: 1. the direction of travel of the ball carrier and tackler(s) 2. the speed of the ball carrier and tackler(s) 3. the direction of the tackle 4. the region struck on both ball carrier and tackler(s) 5. the tacklers head position at T0

If these events can be coded with certainty then coding of the lower level should take place. If the viewing of any specific aspect is obscured, unsure or unknown should be listed for the field.

Using the Tackle Database With the tackle form (F_Tackles) open, you will be able to navigate through all of the tackles that you have coded for the video footage. To code a tackle at the lower level you should click on the ‘add record’ button. This will open the lower level data entry page.

It is important that you do not press the ‘Add record’ button more than once as this will create duplicate data entry forms within the database. Once a record has been created you can view and edit the data coded at the lower level using the ‘view record’ button.

Impact sequence and the lower level data entry page The number of lower level data entry pages, and fields activated, will differ depending on the number of tacklers and the impact sequence that has been coded at the upper level. The lower level form (Figure 4) will always activate with ball carrier (green) and primary tackler (red) fields enabled. The Blue secondary tackler fields will only activate for simultaneous tackles

IRR2 Tackle Coding Manual D-17

Figure 4: The lower level data entry form’s paired analysis of ball carrier and tackler variables. Note that the secondary tackler (blue) fields are only enabled for simultaneous tackles. The record navigation buttons are circled If the tackle coded is a sequential tackle, then the number of lower level records opened will match the number of tacklers identified. You can navigate through these records using the record navigation buttons at the base of the form.

The database should be used with Snapper to navigate for the tackle events identified.

Viewing projects in Snapper The video of each event coded in Snapper is saved with the event list. To view an event, simply double click on it in the event list. Extended footage of the tackle event will play, including 5 seconds of play before and after the tackle. To stop or play the footage, click on the video display window once. You can navigate though frame by frame using the mouse wheel or the arrow keys. Please view the event as many times as you need to, to code the footage correctly.

Remember:

If at any time an event or field can not be evaluated with certainty, it should not be coded. It is important that you only code what you see, not what you think or assume may have happened, even if this is based on playing experience.

If you need help with Snapper at any time, please ask the project manager or view the help file in the admin folder on biomech-15 (C:\IRB Tackle Study\Admin files)

D-18 IRB Tackle Study

General Information with no specific reference time

Jersey Number/Position: The jersey number of both the ball carrier and tackler. Enter ‘0’ if it cannot be seen or if the players do not have jersey numbers (common in schoolboy rugby).

Injury to Ball Carrier: Was there an injury to the ball carrier?

Evasion technique: The ball carrier attempts to evade the tackle before the impact by: 1. Side Step or Swerve (Immediately prior to the point of impact between the tackler and the ball carrier, the carrier attempts to side step the oncoming tackler) 2. Sprint (Immediately prior to the point of impact between the tackler and the ball carrier, the carrier attempts to evade the tackle by sprinting away from the oncoming tackler) 3. Duck (Immediately prior to the point of impact between the tackler and the ball carrier, the carrier attempts to duck below the oncoming tackler) 4. Dummy (Immediately prior to contact, the ball carrier shapes to pass the ball, stopping at arm extension, then retracting ball, continues onwards) 5. Kick (Immediately prior to the tackle, the ball carrier attempts to kick the ball) 6. No Evasion (Immediately prior to the point of impact between the tackler and the ball carrier, the carrier makes no attempt to evade the oncoming tackler) 7. Unsure

Relative Height: The relative standing stature of the ball carrier compared to the tackler. 1. Larger than the tackler 2. Smaller than the tackler 3. A similar size to the tackler 4. Unsure

For a simultaneous tackle, this comparison should be in reference to the primary tackler

Relative Mass: The relative mass of the ball carrier compared to the tackler. 5. Larger than the tackler 6. Smaller than the tackler 7. A similar size to the tackler 8. Unsure

For a simultaneous tackle, this comparison should be in reference to the primary tackler

IRR2 Tackle Coding Manual D-19 Fields to be analysed at T0

Back Straight: The Ball carrier’s Torso was extended to 180o at the time of impact. Observation made at T0. 1. Yes 2. No 3. Unsure

Shoulders Rounded: The Ball carrier’s shoulders were rounded (the player squeezing the ball or in a hunched position) at the time of the impact. Observation made at T0. 1. Yes 2. No 3. Unsure

Feet adjacent/Steps to base: The Tackler gets a leading foot position within approximately 30 cm (an approximate foot length) of any part of the ball carrier’s foot. Observation made at T0. 1. Yes 2. No 3. Unsure

Knees straight: The ball carrier’s knees are extended to 180o when entering the tackle (Ideally the knees should be bent). Observation made at T0. 1. Yes 2. No 3. Unsure

D-20 IRB Tackle Study

Tackle direction: The direction that the tackle is coming from (Figure 5). This is regardless of the Ball carrier’s running direction.

Observation made at T0. 1. Front (from in front of the ball carrier) 2. Behind (from behind) 3. Right Side 4. Left Side 5. None 6. Unsure

Front

Left Right Side Side

BehindRear Figure 5: Direction of tackle (with thanks to Ken Quarrie, NZRU)

IRR2 Tackle Coding Manual D-21 Body Region struck on ball carrier or tackler: The body region which is struck or hit in the main tackle contact (T0). These definitions are displayed on a body chart in Figure 6. Please note that there are separate definitions for the body region struck during ground contact. For these definitions please see page D-34.

Head Skull and mandible Neck Cervical vertebrae and associated areas of the trapezius Chest Area bound by the Clavicles, anterior axillary fold and a line joining the lower margin of the 10th rib Back Posterior surface of torso bounded by the posterior axillary fold, a line joining the superior angles of the scapulae and the iliac crest Abdomen Area bounded the lower margin of the chest (as specified above) and a line joining the anterior superior iliac spines. Shoulder Area bounded by a line joining the coracoid process to the anterior axillary fold to the approximate insertion point of Deltoid Upper limb Area of the upper limb from the lower limit of the shoulder (as specified above) to a line joining the epicondyles of the humerus Forearm and hand Elbow to finger tips Hips Area bounded by a line joining the ASIS and a line joining the Greater trochanter and the hollow of the groin Thigh Area bounded by a line joining the Greater trochanter and the hollow of the groin to the Superior margin of the femoral condyles Knee The Knee joint (femoral condyles to tibial plateau) Lower leg The area of the lower limb distal to the knee joint. Unsure – Upper body The impact obviously occurs to the upper body, but the precise region struck is obscured Unsure – obscured The precise location of the impact is obscured None – Missed tackle The tackler did not make contact with the ball carrier. The event was a missed tackle

This observation is made at T0.

D-22 IRB Tackle Study

Chest (Green) Shoulder

Back Upper Limb

Abdomen (Red)

Forearm and hand Hips (Blue)

Thigh

Knee

Lower Leg

IRR2 Tackle Coding Manual D-23 Figure 6: Body chart showing the definitions of body region for the body region struck during tackle contact.

D-24 IRB Tackle Study

Head and neck position: The main position of the head and neck at impact. Observation made at T0. 1. Head up (Head/neck in a neutral or extended position relative to the trunk) 2. Chin on chest (Head/neck in a flexed position) 3. Unsure

Stance height: The viewer’s impression of the Ball carrier’s body posture. Observation made at T0. 1. Low (small compact body shape) 2. High (long/tall body shape, no abdominal or lower limb flexion) 3. Falling/Diving 4. Unsure

Head position in tackle The position of the tackler’s head in relation to the ball carrier. Observation made at T0. (Figure 7) 1. Above The tackler’s head is above the ball carrier’s body (especially for a smother tackle) 2. Behind The tackler’s head is behind the ball carrier’s body with reference to their direction of travel 3. In front The tackler’s head is in front of the ball carrier’s body with reference to their direction of travel 4. Beside The tackler’s head is beside the ball carrier’s body with reference to their direction of travel 5. Unsure The head position of the tackler is obscured

Above Behind In front Beside

Figure 7: Head position of the tackler during the tackle contact showing a head position above, behind, in front and beside.

IRR2 Tackle Coding Manual D-25 Fields to be analysed 5 frames or more before the tackle impact (T<-5)

Steps into tackle: The player takes a step forward leading into the tackle event. Observation made before T-5. 1. Yes 2. No 3. Unsure

Was the ball carrier supported? The Ball carrier has support players that they could have passed/offloaded to. Observation made before T-10. 1. Yes 2. No 3. Unsure

Aware of the tackler: The tackler is within the Ball carrier’s field of view or has been sighted by the ball carrier. Observation made before T-5. 1. Yes 2. No 3. Unsure

Fields to be analysed over a specified period from 10 frames before the tackle impact (T-10 to T0 or T5)

Speed of Ball Carrier/Tackler: The viewer’s impression of the speed of the ball carrier. Observation made over the period T-10 to T0. 1. Still/Stationary (No ground translation) 2. Slow (i.e. jogging) 3. Fast (i.e. sprinting) 4. Unknown

Direction of travel: The direction of travel of the players using a co-ordinate axis system based on the main direction of travel prior to impact. The axes are applied globally for the ball carrier. Observation made over the majority of the period T-10 to T0. x The y axis runs down the length of the field parallel to the sideline. Ball Carrier movement towards the opposition’s try line is positive. x The x axis runs across the field parallel with the try line. Movement towards the right sideline is positive x, towards the left sideline is negative x.

Therefore a value of (x, y) for the ball carrier indicates diagonal movement to the right and towards the try line. A value of (x, 0) indicates the player is traversing across the field to the right. Finally a value of (x, -y) indicates the ball carrier is moving diagonally, right and back towards his try line.

D-26 IRB Tackle Study

Important!! Please Note: the coordinate axis system and direction (positive and negative) is the same for describing the ball carrier and tackler.

y

x

T1

T2 BC = 0,y T1 = -x,-y BC T2 = x,0

Figure 8: The rugby field, showing a co-ordinate axis system and the direction of travel for the ball carrier and two tacklers based on these axes.

b)

c)

d)

e)

f)

g)

h)

i)

j) y y k) x x l) Figure 9: An example of direction of travel evaluation using co-ordinate axes. In this situation, the ball carrier’s direction of travel is (x, y) and the tackler’s direction of travel is (x, -y).

IRR2 Tackle Coding Manual D-27 Body orientation of Ball Carrier: The body orientation of the ball carrier with reference to the direction of travel. Observation made over the majority of the period T-10 to T0. 1. Front (the ball carrier is facing the direction of travel, i.e. He is running forwards) 2. Behind (the ball carrier has their back to the direction of travel, i.e. He is running backwards) 3. Right Side (the ball carrier is side on to the direction of travel) 4. Left Side (the ball carrier is side on to the direction of travel) 5. Unsure 6. Not Applicable. The Ball carrier is stationary.

Small steps in contact: Does the Ball carrier take small steps while held in the tackle contact? Observation made over the majority of the period T–10 to T5. 1. Yes 2. No 3. Unsure

Eyes on ball carrier: The tackler has their eyes on the ball carrier. This observation is made over the majority of the period T-10 to T0. 1. Yes 2. No 3. Unsure

Feet Preparation: The tackler’s feet movement prior to the tackle. Observation made over the period T– 10 to T0. 1. Small Steps 2. Wide Steps 3. No Movement 4. Unsure

D-28 IRB Tackle Study

Fields to be analysed over a specified period from 5 frames before the tackle impact (T-5 to T0 or T5)

Ball Carry Method: The ball carry method employed by the ball carrier. Observation made over the period T-5 to T0 1. Lead Arm (Ball carried by the arm on the impact side) 2. Following arm (Ball carried by the arm on the opposite side) 3. Two hands (Ball in two hands or passing with two hands) 4. Unsure

Tackle Bust method: The ball carrier attempts to break the tackle contact by employing one of the methods listed below: 1. Shoulder bump (At point of impact between the tackler and the ball carrier, the carrier attempts to turn their shoulder into the oncoming tackler and bump them) 2. Ball bump (At point of impact between the tackler and the ball carrier, Ball Carrier wraps ball to chest and attempts to bump the tackler using the ball for impact) 3. Hit and Spin (At the point of impact between the tackler and the ball carrier, Ball Carrier spins off the tackler in an attempt to break the tackler’s grasp) 4. Hand Off (Physical push away or down) 5. Arm Fend (use of arm to fend, or act as a buffer pre contact) 6. Hip Bump (At the point of impact between the tackler and the ball carrier, Ball Carrier attempts to bump the oncoming tackler with their hip / thigh area) 7. High Knees (At the point of impact between the tackler and the ball carrier, the carrier attempts to evade the oncoming tackler by accentuating a high knee lift in their run stride) 8. No Evasion (At the point of impact between the tackler and the ball carrier, the carrier makes no attempt to evade the tackler) 9. Unsure

Observation made over the period T–5 to T5

IRR2 Tackle Coding Manual D-29 Feet alignment: The feet alignment of the tackler (Figure 10). It can be: 1. Splayed (One foot in front of the other with reference to the opponent) 2. Parallel (Feet side by side) 3. Unsure

Observation made at T-5 to T0.

m)

n)

o)

p)

q)

r) Figure 10: Feet position in tackle. The Tackler’s feet are aligned parallel; the Ball Carrier’s feet are splayed.

Stance width/length: The approximate stance width/length of the tackler. Observation made at T-5 to T0. 1. Feet shoulder width or greater 2. Feet less than shoulder width 3. Only one, or no feet contact 4. On knees 5. Unsure

Lower body position than Ball Carrier? The tackler adopts a lower body position than the ball carrier (with reference to the line of the shoulders). Observation made over the majority of the period T–5 to T0. 1. Yes 2. No 3. Unsure

D-30 IRB Tackle Study

Fields to be analysed after the tackle impact leading up to ground contact

Ball Carrier lifted by tackler: The ball carrier is lifted from ground contact by a tackler. Observation made between T0 and ground impact. 1. Yes 2. No 3. Unsure

Direction after impact: The direction of travel of the ball carrier after/in the tackle using a co-ordinate axis system. The axes are applied in the same manner as for direction of travel prior to the tackle. Observation made over the period T0 to T10. x The y axis runs down the length of the field parallel with the sideline. Movement towards the opposition’s try line is positive. x The x axis runs across the field parallel with the try line. Movement towards the right sideline is positive x, towards the left sideline is negative x.

yx

yx

T2 T1

BC

Post tackle (0, -y)

Figure 11: The rugby field, showing a co-ordinate axis system and the direction of the tackle unit (ball carrier, and tacklers) after impact.

IRR2 Tackle Coding Manual D-31 Arms Grapple: The tackler wraps their arms around, and holds on to, the ball carrier. Observation made over the period T0 to T10. 1. Yes 2. No 3. Unsure

Extends lower body: Extension of the lower limb during the tackle contact is apparent. Observation made over the period T0 to T5. 1. Yes 2. No 3. Unsure

Secondary impact with another tackler? Did the tackler collide unintentionally with another tackler? Observation made at any time after T0 until a ruck or maul is formed. 1. Yes 2. No 3. Unsure

Was there a ground impact for the Ball Carrier/tackler? 1. Yes 2. No

D-32 IRB Tackle Study

Ground Contact

Striking object: The striking object during the secondary impact. 1. Ground 2. Goal Post 3. Fixed Object 4. Spectator 5. Referee 6. Other 7. Unknown 8. Not applicable

Region Struck: The main regions struck during the secondary impact. Up to three regions may be listed in sequential order.

Head 1. Head and neck 2. Neck Shoulder 3. Anterior trunk Anterior trunk 4. Posterior trunk 5. Shoulder Upper Posterior 6. Upper limb limb trunk 7. Thigh Hips 8. Knee (Blue) 9. Lower leg Thigh 10. Unsure Knee Lower Leg

Falling body posture: The falling body posture of the player: 1. Vertical/long/unrelaxed (the player is in an extended rigid position) 2. Small (the player is a flexed or compact body position) 3. Unsure

Final position of tackle: The final position of the ball carrier and tackler on the ground upon coming to rest. 1. Tackler on top 2. Ball carrier on top 3. Fell separately 4. Both on feet 5. Ball carrier on ground, tackler on feet 6. Other/unsure 7. No fall/Not applicable

Injury associated with ground impact? In your opinion, is the fall responsible for any injury sustained by the ball carrier or tackler? 1. Yes 2. No

D-34 IRB Tackle Study

Specific factors: Observation of any of the following factors? (Yes/No) 1. Impact to head/neck 2. Fall onto thorax/shoulder 3. Fall onto back/buttocks 4. Crush (eg. Player crushed between ground and tackler) 5. Lifted & turned (spear tackle) 6. Fall resulting in axial loading of limb (Fall onto elbow or outstretched hand) 7. Did the motion exceed normal joint range of motion 8. Did the tackler contribute to the load experienced by the ball carrier 9. Foot/lower limb locked and upper body twisting 10. Was the limb associated with the loaded region prevented from moving freely? (eg, tackler laying on a Ball Carrier’s foot or ground contact forcing joint into extreme range)

Additional notes field: Additional comments about the ground impact specifically field variables not covered in the protocol should be noted in the additional notes field.

IRR2 Tackle Coding Manual D-35 B. Summary of Timing of analysis

Variables evaluated at T0 Field Time Tackle Type T0 Sequence T0 BC Back Straight T0 BC Shoulders Rounded T0 BC Knees bent T0 BC Region Struck T0 BC Tackle direction T0 BC Head and neck position T0 BC Body height T0 T Back Straight T0 T Feet adjacent/Steps to base T0 T Knees bent T0 T Region Struck T0 T Head and neck position T0 T Body height T0 T Head position in tackle T0

Variables evaluated within -5 frames of T0 Field Time BC Ball Carry Method T0-5to T0 T Lower body position T0-5to T0

Variables evaluated within -10 frames of T0 Field Time BC Speed T-10 to T0 BC Direction of travel T-10 to T0 BC Body orientation T-10 to T0 T Eyes on ball carrier? T-10 to T0 T Feet Preparation T-10 to T0 T Speed T-10 to T0 T Direction of travel T-10 to T0 T Body orientation T-10 to T0 BC Aware of the tackler? T< T-5 BC Steps into tackle T< T-5 T Steps into tackle T< T-5 BC Small steps in contact T-10 to T5 Tackle bust method T-5 to T5

Variables evaluated prior to -10 frames of T0 Field Time BC Was the ball carrier supported? T0< T-10

D-36 IRB Tackle Study

Variables evaluated after T0 (note specific reference time) Field Time T Extends lower body T0 to T5 BC Direction after impact T0 to T10 T Arms Grapple T0 to T10 T Direction after impact T0 to T10 BC Ground Contact T0+ T Ground Contact T0+ T Secondary impact with another tackler > T0 BC Lifted by tackler > T0,

IRR2 Tackle Coding Manual D-37 Fields with no specific analysis time Field Time Event Type na Injury na Field Half na Field Corridor na Field Aisle na Counter ID na Player number/position na BC’s team na Grade na Tackler’s team na Relative height na Relative mass na Ground dry? na Raining? na Winning? na Attempting to score na Phase Before na Tackle complete/IRB Tackle na Not Tackle na Phase of play After na BC Ground Striking object na BC Ground Region Struck na BC Ground Final position of tackle na BC Ground Side of fall na BC Ground Region loaded na BC Ground Injury associated with ground impact? na BC Ground Range of motion exceeded na BC Ground Limb motion retarded na BC Ground Loading pattern of main region affected na BC Ground Specific factors na BC Ground Falling position na BC Ground Falling na BC Ground Tackler contributed to the magnitude of load na T Ground Striking object na T Ground Region Struck na T Ground Final position of tackle na T Ground Region loaded na T Ground Injury associated with ground impact? na T Ground Range of motion exceeded na T Ground Limb motion retarded na T Ground Loading pattern of main region affected na T Ground Specific factors na

D-38 IRB Tackle Study

Fields with no specific analysis time (continued) T Ground Falling position na Impact force na Tackler’s jersey number na BC Evasion na Number of Tacklers na Coded further na Retains ball na

IRR2 Tackle Coding Manual D-39 Study Checklist x Locate the MS Access database assigned to you on Biomech-15. The database is saved as:

IRR2TackleDB_YOURNAME.mdb

x All coding for the study needs to be recorded in this database. Click on ‘Add upper level coding’ to complete the coding for the tackles that you have identified.

x For events which can also be coded at the lower level, click on the ‘add record’ button on the form F_Tackles. The lower level coding form, including the ground contact form will then open.

x When you have completed coding the tackles that you have identified from the footage, click on the “review lower level coding” button on the switchboard. This will display all of the tackles that you have identified with the coding details that have been completed. Please ensure that you have coded all tackles at the lower level where it was possible to do so.

D-40 IRB Tackle Study

APPENDIX E

GRAPHICAL USER INTERFACES FOR THE UPPER

AND LOWER LEVEL ANALYSES FROM THE TACKLE

DATABASE

303

Graphical user interface for upper level analysis from the Tackle Study Database (used in IRR2)

Graphical user interface for the lower level analysis from the Tackle Study Database (used in IRR2)

305

306 APPENDIX F

PROPORTION OF COMPLETE FIELDS IN THE

RESULTS OF AN ANALYSIS OF A SAMPLE OF 100

TACKLES

307 Analysislevel FieldName % Upperlevelfields TackleID 0 EventType 0 GameID 0 LevelID 0 Countercode 0 Position 0 Ballcarriersteam 0 Tacklingplayersteam 0 Tackletype 0 Numberoftacklers 0 ImpactSequence 0 TackleComplete 0 Ifnotatacklewhatoccurred? 0 Tacklecodedatthelowerlevel 0 PhaseBeforeID 0 PhaseAfterID 0 Retainsball 0 FieldHalfID 0 FieldAisleID 0 FieldCorridorID 0 ImpactForce 0 GroundDry 0 Raining 0 Attemptingtoscore 0 FinalScore 0 Supplementaryinjuryeventanalysis 0 Playeraffectedorinjuredinmedicalevent 0 InjuryID 0 Missedgameinjury 0 UpperLevelAnalysisNotes 0 Lowerlevelfields TacklePairIdentificationNumber 0 TacklePairNum(databasemanagementfield) 0 TacklePairNotes 0 Lowerlevel BallCarriersPosition 0 description EvasionID 6 RelativeHeightofballcarrierandtackler 11 RelativeMassofballcarrierandtackler 11 TacklerPosition 0 SecondTacklerPosition 0 LowerLevel Awareoftackler 26 BallͲcarrier Supported 20 BCSpeed 6 BCDirection 6

308 Analysislevel FieldName % BCBallCarryMethod 6 Lowerlevelfields BCOrientation 6 Ballcarrier BCBackStraight 10 BCShouldersRounded 12 BCSteps 20 BCKneesStraight 12 TackleDirection 7 BCLifted 7 BCRegionStruck 7 BCHeadNeckPos 7 BCHeight 7 BCSmallSteps 8 BCDirectionAfter 6 BCTackleBustMethod 6 BCGroundContact 0 Lowerlevel Aware 7 Tackler Speed 6 Direction 7 Orientation 7 BackStraight 10 LowerBodyPos 8 FeetAlignment 6 StanceWidth 6 Steps 13 KneesStraight 11 FeetPreperation 7 ExtendsLowerBody 9 ArmsGrapple 10 HeadInTackle 8 BodyRegionStruck 7 HeadNeckPos 7 Height 7 DirectionAfter 7 SecondaryImpact 28 GroundContact 0 Lowerlevel Aware 3 Secondtackler Speed 2 Direction 2 Orientation 2 BackStraight 3 LowerBodyPosition 2 FeetAlignment 2 StanceWidth 2

309 Analysislevel FieldName % Steps 4 Lowerlevel KneesStraight 4 Secondtackler FeetPreperation 2  ExtendsLowerBody 2  ArmsGrapple 2  HeadInTackle 2  BodyRegionStruck 2  HeadNeckPos 2  Height 2  DirectionAfter 2  SecondaryImpact 2  GroundContact 0 Groundcontact GroundcontactID 0 Groundcontactnotes 0 Groundcontact BallCarrierStikingObject 2 Ballcarrier BallcarrierRegionStruck1 3 BallcarrierRegionStruck2 4 BallcarrierRegionStruck3 7 Ballcarrierfallingposition 3 Ballcarrierinjury 0 AxialloadingtoBC 0 HeadorneckimpacttoBC 0 Falltothoraxorshoulder 0 fallstobackorbuttocks 0 lowerlimblockedupperbodytwisting 0 limbinjuredfreemovementprevented 0 liftedandturned 0 MotionexceedsnormalROM 0 Tacklercontributestoload 0 crushed 0 fallingposture 3 Groundcontact TacklerStikingObject 0 Tackler TacklerRegionStruck1 1 TacklerRegionStruck2 1 TacklerRegionStruck3 7 Tacklerfallingposition 1 Tacklerinjury 0 AxialloadingtoTackler 0 HeadorneckimpacttoTackler 0 TacklerFalltothoraxorshoulder 0 Tacklerfallstobackorbuttocks 0 Tacklerlowerlimblockedupperbodytwisting 0 Tacklerlimbinjuredfreemovementprevented 0

310 Analysislevel FieldName % Tacklerliftedandturned 0 Groundcontact TacklerMotionexceedsnormalROM 0 Tackler Tacklercontributestoload 0 Tacklercrushed 0 Tacklerfallingposture 2 Groundcontact Tackler2StikingObject 0 Secondtackler Tackler2RegionStruck1 0 Tackler2RegionStruck2 0 Tackler2RegionStruck3 0 Tackler2fallingposition 0 Tackler2injury 0 AxialloadingtoTackler2 0 HeadorneckimpacttoTackler2 0 Tackler2Falltothoraxorshoulder 0 Tackler2 fallstobackorbuttocks 0 Tackler2lowerlimblockedupperbodytwisting 0 Tackler2limbinjuredfreemovementprevented 0 Tackler2liftedandturned 0 Tackler2MotionexceedsnormalROM 0 Tackler2contributestoload 0 Tackler2crushed 0 Tackler2fallingposture 0 

311