BIOMECHANICAL ANALYSIS OF ELITE RACE WALKING BRIAN STEPHEN HANLEY A thesis submitted in partial fulfilment of the requirements of Leeds Metropolitan University for the degree of Doctor of Philosophy May 2014 ABSTRACT The aim of this study was to provide a comprehensive analysis of key biomechanical variables in race walking through the analysis of elite athletes in both competitive and laboratory settings. Video data from two 3CCD camcorders of athletes competing over 10 km (juniors only), 20 km, and 50 km were collected at three international competitions. For the 20 km and 50 km events, multiple recordings were made to identify if kinematic changes occurred. In addition, synchronised high- speed video, electromyography and ground reaction force data were collected of 20 elite race walkers in a laboratory setting and combined to calculate joint moments, power and work. The key discriminants with regard to better performances were long step lengths and high cadences, and the contribution made by flight distance to step length (approximately 13%) was particularly important, regardless of race distance or age category. Step length ratio was a better predictor of optimum step length than absolute values and a ratio of about 70% was found in the fastest athletes. Although reductions in step length and flight distance were a major cause of decreased speed over both 20 km and 50 km, many gait variables did not alter greatly, showing that these elite athletes were able to maintain their techniques despite fatigue. The foot position ahead of the body at initial contact (approximately 20% of stature) need not be detrimental to fast walking if the athlete has the strength to overcome the potentially negative effects; instead, it can be beneficial to increase this distance in achieving a greater step length and could be a key area for women in particular to develop. The hip muscles were the main source of energy generation, with both flexors and extensors doing more positive work than any other muscle group (22.4 ± 7.1 J and 42.3 ± 10.1 J respectively), although the ankle plantarflexors also generated considerable energy before toe-off (16.4 ± 3.8 J). A hip extensor moment that occurred during late swing and early stance helped maintain forward momentum as it reduced the braking peak force and duration of the negative anteroposterior force. The knee had little involvement in energy generation because of its predominant role as a rigid lever during stance, and absorbed considerable energy during swing (–46.4 ± 9.5 J). However, its abnormal movement that was dictated by the race walking rule also had an important role in maintaining contact with the ground and reducing vertical forces so that visible loss of contact was avoided. The study was the first to analyse in such depth the biomechanics of elite male and female race walkers across all competitive distances and its results could be used to develop a technical manual for this Olympic event and greatly impact on coaching practice. DECLARATION I confirm that the thesis is my own work; and that all published or other sources of material consulted have been acknowledged in notes to the text or the bibliography. I confirm that the thesis has not been submitted for a comparable academic award. ACKNOWLEDGEMENTS I would like to sincerely thank my Director of Studies, Dr Athanassios Bissas, for all his help and support throughout the whole process that was so vital to the quality of this final submission and the published articles. I would also like to thank my Supervisor, Dr Andrew Drake, for all his assistance and especially with regard to the recruitment of so many high-standard race walkers from around the world. In addition, his help with data collection at the international competitions was invaluable. I want to give special thanks to the international coaches who helped to arrange for so many of their athletes to travel to Leeds, in particular Michael Lane, National Event Coach (Ireland) who has consistently supported the work done for this study. The feedback on the data and interpretation from all coaches who got involved was extremely useful in directing the study’s path. I would also like to thank Dr Ian Richards who was also a great help in arranging data collection and travel, especially at the 7th European Cup Race Walking in Royal Leamington Spa. Thank you to all the athletes who took part in the studies, and especially those who had to travel great distances to volunteer their time and efforts. The study was greatly enhanced by the quality of these world-class athletes. In addition, I would like to thank the members of staff and students at Leeds Metropolitan University who assisted with data collection. Finally, I would like to dedicate this thesis to Rosie and Ronan who were always there to give a helping hand or critical eye. TABLE OF CONTENTS Abstract iii Declaration iv Acknowledgements v 1. Introduction 1 1.1 History of race walking 2 1.2 Elite performances in race walking 3 1.3 Definition of race walking 3 1.4 Prior biomechanical research in race walking 6 1.5 Purpose and prospects of the research 10 2. Literature Review 11 2.1 Introduction 12 2.2 Hierarchical model of race walking 13 2.3 Physiques of race walkers 16 2.3.1 Leg length relationships 16 2.3.2 Reported anthropometric measurements 18 2.4 Step length and cadence 20 2.4.1 Step length correlations 22 2.4.2 Step length ratio 22 2.4.3 Changes in step length and cadence with changes in speed 24 2.5 Position of the foot in relation to the centre of mass 29 2.5.1 Foot ahead and foot behind 29 2.6 Step time 32 2.6.1 Contact time and flight time 32 2.6.2 Maintenance of double support 33 2.6.3 Visible loss of contact 34 2.6.4 Stance to swing ratio 35 2.7 Posture 37 2.7.1 The lower limb joints 37 2.7.1.1 The knee joint 37 2.7.1.1.1 The straightened knee rule in race walking 37 2.7.1.1.2 Knee angle during stance 38 2.7.1.1.3 Knee angle during swing 40 2.7.1.2 The hip joint 41 2.7.1.3 The ankle joint 43 2.7.2 The upper limb joints 45 2.7.3 Pelvic and shoulder girdle movements 48 2.7.3.1 Pelvic girdle rotation 48 2.7.3.1.1 Stride width 49 2.7.3.2 Shoulder girdle rotation 50 2.7.3.3 Distortion angle 52 2.7.3.4 Pelvic obliquity 52 2.8 Vertical displacement in normal and race walking 55 2.9 Race walking kinetics 57 2.9.1 GRF patterns in normal walking 57 2.9.2 GRF patterns in race walking 58 2.10 Muscular activity 62 2.11 Joint moments and powers 66 2.12 Injuries 72 2.13 Summary of key points 74 2.13.1 Limitations of previous research 77 2.13.2 Rationale for the present study 78 2.13.3 Aim of the present study 79 2.13.4 Objectives of the present study 79 3 Methods 80 3.1 Introduction 81 3.2 Outdoor studies 81 3.2.1 The World Race Walking Cup 82 3.2.2 The European Cup Race Walking 83 3.2.3 Data collection 84 3.2.4 Data analysis 86 3.2.4.1 Body segment parameter models 87 3.2.4.2 Filtering and reliability analysis 90 3.2.4.3 Definitions of measured variables 92 3.2.5 Statistical analysis 94 3.3 Laboratory study 95 3.3.1 Data collection 95 3.3.1.1 GRF data collection 96 3.3.1.2 High-speed video data collection 97 3.3.1.3 EMG data collection 99 3.3.2 Data analysis 102 3.3.2.1 GRF data analysis 102 3.3.2.2 High-speed video data analysis 105 3.3.2.3 Calculation of muscle moments, powers and work 107 3.3.2.4 EMG data analysis 108 3.3.3 Statistical analysis 108 4 Study 1: 20 km Competitions 110 4.1 Introduction 111 4.2 Methods 112 4.2.1 Participants 112 4.3 Results 114 4.3.1 World Cup data 114 4.3.1.1 Speed, step length and cadence 114 4.3.1.2 Relative position of the foot at initial contact and toe-off 118 4.3.1.3 Contact time and flight time 119 4.3.1.4 Stance:swing ratio 120 4.3.1.5 Vertical displacement 120 4.3.1.6 Pelvic and shoulder girdle rotation 120 4.3.1.7 Knee joint angles 121 4.3.1.8 Hip and ankle joint angles 121 4.3.1.9 Shoulder and elbow joint angles 125 4.3.1.10 Analysis of individual athletes 126 4.3.2 European Cup variation data 128 4.3.2.1 Speed, step length and cadence 128 4.3.2.2 Contact time and flight time 132 4.3.2.3 Pelvic and shoulder girdle rotation 132 4.3.2.4 Knee, hip and ankle joint angles 134 4.3.2.5 Shoulder and elbow joint angles 134 4.3.2.6 Analysis of individual athletes 135 4.4 Discussion 139 4.4.1 Predictors of faster race walking 139 4.4.2 Kinematic variations during 20 km race walking 142 4.5 Conclusion 145 5 Study 2: 50 km Competitions 147 5.1 Introduction 148 5.2 Methods 148 5.2.1 Participants 148 5.3 Results 150 5.3.1 World Cup data 150 5.3.1.1 Speed, step length and cadence 150 5.3.1.2 Foot positioning, foot movement and flight distance 153 5.3.1.3 Changes in velocity during foot ahead and foot behind 154 5.3.1.4 Stance:swing ratio 154 5.3.1.5 Vertical displacement 154 5.3.1.6 Knee, hip and ankle joint angles 155 5.3.1.7 Shoulder and elbow joint angles 156 5.3.1.8 Pelvic and shoulder girdle rotation 156 5.3.1.9 Individual analysis of athletes 158 5.3.2 European Cup variation data 159 5.3.2.1 Speed, step length and cadence 159 5.3.2.2 Temporal variables and foot positioning 160 5.3.2.3 Angular data – lower limb 161 5.3.2.4 Angular data – upper limb 162 5.3.2.5 Angular data – upper body rotation 163 5.3.2.6 Analysis of individual athletes 164 5.3.2.7 Correlation changes with distance walked 166 5.4 Discussion 171 5.4.1 Predictors of faster race walking 171 5.4.2 Kinematic variations during 50 km race walking 173 5.5 Conclusion 176 6 Study 3: Junior 10 km Competitions 178 6.1 Introduction 179 6.2 Methods 179 6.2.1 Participants 179 6.3 Results 181 6.3.1 Speed, step length and cadence 181