Biomechanical Considerations in Goal- Kicking Accuracy: Application of an Inertial Measurement System
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Biomechanical Considerations in Goal- Kicking Accuracy: Application of an Inertial Measurement System A thesis submitted in fulfilment of the requirements of the degree of DOCTOR OF PHILOSOPHY Stephanie J. Blair MSc 2019 Victoria University College of Sport and Exercise Science Institute for Health and Sport (IHES) Melbourne, Australia Principle Supervisor: Dr Kevin Ball Associate Supervisors: Dr Grant Duthie Dr Sam Robertson Abstract Goal-kicking is an important skill in Australian Football (AF), accounting for approximately 62% of points scored during a match (Anderson et al., 2018). Despite its importance, little biomechanical research has examined the key technical characteristics underpinning the skill. The aims of this thesis were to validate a methodological approach to enable quantification of goal-kicking kinematics in a field environment, and examine goal-kicking technique and identify technical factors associated with accuracy. In Chapters 3 and 4, the Xsens inertial measurement system (IMS) was validated against a Vicon motion capture system (MAS) when measuring lower extremity and pelvis kinematics. Trivial to small mean differences (0.2-10.1%) and measurement error (0.1-7.9%) were found between the IMS and MAS across all parameters, advocating the use of IMS to quantify kicking kinematics. In Chapter 5, the effect of modifying the task constraints on accurate goal-kicking was explored. Increasing the distance of the shot from goals (30 m to 40 m) required substantially greater joint range of motion (knee and hip), with higher linear (foot speed) and angular (knee and shank) velocities. Altering the angle of the shot (0 to 45°) had no substantial influence on accurate goal-kicking technique. Findings indicated adjustments in goal-kicking technique may be required dependent on the location of the shot. In Chapter 6, 18 elite to sub-elite AF players performed 15 x 30 m goal-kicks in-front of goals and technique was examined on group-basis. A number of substantial kinematic differences were identified between accurate and inaccurate goal-kicks. For example, accurate goal-kicks were characterised by substantially less kick-leg joint range of motion (ankle, knee and hip), lower linear (com, foot speed) and angular (knee and shank) velocities, with less support-leg knee flexion during the kicking phase. In addition, a number of substantial linear and quadratic relationships were reported between technical parameters and accuracy. Findings indicated that many factors influence goal-kicking accuracy in AF; ranging from technical errors in the player’s approach, configuration of their support-leg and kick-leg motions, through to follow-through position. In Chapter 7, goal-kicking data from chapter 6 was examined on individual-basis. All players demonstrated substantial kinematic differences between accurate and inaccurate goal-kicks, along with substantial relationships between kinematic parameters and accuracy, but these were individual-specific. A combination of both a group and individual-based analysis provided a more thorough understanding of technical factors which influence goal-kicking technique in AF. The body of work in this thesis provides: 1) validation of a methodological approach to quantify kicking biomechanics, and 2) a comprehensive understanding of technical factors associated with goal-kicking accuracy in AF, and 3) recommendations for both research and coaching practice. ii Declaration Doctor of Philosophy Declaration I, Stephanie Jayne Blair declare that the PhD thesis entitled “Biomechanical Considerations in Goal-kicking Accuracy: Application of an Inertial Measurement System” is no more than 100,000 words in length including quotes and exclusive tables, figures, appendices, bibliography, references and footnotes. This thesis contains no material that has been submitted previously, in whole or in part, for the award of any other academic degree or diploma. Except where otherwise indicated, this thesis is my own work. Signature: Date: 01/03/2019 iii Acknowledgements Firstly, I would express my sincere gratitude to my principle supervisor, Kevin Ball, for all your support, advice, guidance and continuous encouragement throughout this process. I have learnt so much from you and have thoroughly enjoyed our countless discussions - even if there was a ‘language’ barrier at times. Thank you for giving me this opportunity and I will be forever grateful for the time you dedicated to helping me through it! I would also like to extend my thanks to my associate supervisors, Grant Duthie and Sam Robertson, your insightful comments have been so invaluable throughout the process. To Robert Stokes, thank you for all your technical assistance throughout the process. You will be greatly missed! To Will Hopkins, thank you for all your statistical guidance throughout my PhD and challenging me to think beyond NHST. To all my participants, thank you for your commitment and willingness to wear a Lyrca suit. This research would not have been possible without you. To my colleagues in PB201, I am so glad I had you all to share the same struggles with, celebrate the highs, complain about the lows and laugh lots with. To Briar and Jill, thank you for being such great friends and continually reminding me that ‘I’ve got this’! And to the girls, Alex, Alice, Kristal, Dani and Suus, I am so thankful for the memories, coffees and laughs we shared, plus the great friendship we have now. To my family, thank you for all your support, encouragement and always believing in me over the last eight years. A Bachelors, Masters and a PhD later, you have made the whole process so rewarding and would not have been possible without you. And finally to Darren, you have been with me throughout every stage of this process, whether it was supporting me through every stressful moment, listening to me complain, celebrating the highs or acting as a guinea pig for each study. Thank you for all your help and support. We did it! iv List of Publications and Awards Publications The following work has been presented at scientific conferences and/or is published in peer-reviewed journals in support of this thesis: Chapter 3 & 4 • Blair, S., Duthie, G., Robertson, S., Hopkins, W. & Ball, K. (2018). Concurrent Validation of an Inertial Measurement System to Measure Kicking Biomechanics in Four Football Codes. Journal of Biomechanics, 17, 24-32. • Blair, S., Duthie, G., Robertson, S., & Ball, K. (2017). Validity of Wearable technologies to measure kicking biomechanics. XXVI Congress of the International Society of Biomechanics, Australia, 23-27th July. • Blair, S., Robertson, S., Duthie, G. & Ball, K. (2016). Validation of wearable technologies to measure goal-kicking biomechanics in Australian Rules Football. 10th Australasian Biomechanics Conference, Australia, 4-6th Dec. Chapter 5 • Blair, S., Robertson, S., Duthie, G., & Ball, K. (2018). The effect of altering distance on goal-kicking technique in Australian Football. 36th International Society on Biomechanics in Sports Conference, New Zealand, 10-14th September. • Ball, K. & Blair, S. (2018). Shot success and kinematic differences with altering kicking angle on goal-kicking technique in Australian football. 36th International Society on Biomechanics in Sports Conference, New Zealand, 10-14th September. Chapter 6 & 7 • Blair, S., Duthie, G., Robertson, S., & Ball, K. (2017). Biomechanics of goal-kicking accuracy in Australian Football using an inertial measurement system. 35th International Society on Biomechanics in Sports Conference, Germany, 14-18th June. v Invited talks • Blair, S. (2017). Talk entitled: Application of the Xsens MVN link system: Australian Football, Rugby Codes & Soccer. Presented during the Xsens session. XXVI Congress of the International Society of Biomechanics, Australia, 23-27 July. Media • Herald Sun article: How to kick goals: Answering footy’s biggest question (page 10: 2/6/2018) • Biomechanics kicking analyst on the Women’s AFL Footy Show: Spearheads (Episode 6: 5/3/2018) • Biomechanics kicking analyst on the Women’s AFL Footy Show: High- Performance match-up (Episode 6: 12/3/2017) Awards • Best student submission in the International Biomechanics Day 2018 2-minute tweet competition for the International Society of Biomechanics in Sport. • Recipient of the International Society of Biomechanics in Sports Conference Student Travel Grant, 2018 • Recipient of the International Society of Biomechanics in Sports Conference Student Travel Grant, 2017. • ISEAL HDR Poster presentation award. • 2015 - 2018 Victoria University International Postgraduate Scholarship. vi Table of Content Abstract..........................................................................................................................ii Declaration ....................................................................................................................iii Acknowledgements........................................................................................................iv List of publications and Awards.....................................................................................v Table of Contents...........................................................................................................vii List of Figures................................................................................................................xii List of Tables.................................................................................................................xvi List of Abbreviations.....................................................................................................xix