RESISTIVE FORCES AND TECHNIQUE ANALYSIS IN FRONT CRAWL SPRINT SWIMMING

Transcription

1 RESISTIVE FORCES AND TECHNIQUE ANALYSIS IN FRONT CRAWL SPRINT SWIMMING By Gina Belinda Dare Sacilotto B. App. Sci. (Exercise and Sport Science) B. Health Sci. (Hons.) This thesis is submitted in fulfilment of the requirements for the completion of the degree of Doctor of Philosophy in Health Faculty of Health University of Canberra Locked Bag 1 University of Canberra Australian Capital Territory, 2617 Australia Submitted in June 2014

2 Abstract Free swimming is the main component of a swim performance and is the most complex to understand. Using the Assisted Towing Method (ATM), developed at the Australian Institute of Sport, this thesis was designed to investigate resistive forces (active drag) and how this method could be integrated into the assessment of free swimming technique. Four investigations were conducted to assess the ATM protocol for integration as an objective assessment tool for coaches, scientists and athletes in front crawl sprint swimming. The aim of study 1 was to examine the reliability of the mean active drag values collected using the ATM. Results indicated that towing the swimmers whilst permitting intrastroke fluctuations (ICC = 0.94, ) allowed the swimmer to produce a higher level of reliability values than when being towed with a constant velocity (ICC = 0.83, ). A considerably lower amount of percentage error was found in the fluctuating trials (CV TE % = 12.6) than the constant trials (CV TE % = 35.0). The aim of study 2 was to compare the stroke mechanics (stroke lengths and rates) of a free swim and an assisted tow trial to determine whether the ATM protocols alter stroke mechanics. Results indicated a significant increase in stroke lengths and rates occurred when swimmers completed the ATM protocol. However, the ratio of stroke length and stroke rate in the assisted condition was found to significantly predict ratios of stroke mechanics in free swimming (r = 0.95). It was concluded that when using the ATM protocol it is possible to transfer technique critiques found in assisted swimming and apply them to free swimming. The aim of study 3 was to investigate instantaneous active drag force-time profiles and deconstruct them into stroke phases. The total sample was split into groups to identify differences between male and female, and elite and sub-elite swimmers. A consistent biphasic curve was found between all elite swimmers and stroke phases could be identified within a profile. The sub-elite group, however, iii

3 produced multiphasic curves which could be linked to anthropometric differences, slower velocities, or inconsistent propulsion generation during the propulsive stroke phases. The aim of the final study, study 4, was to quantify technique through the use of a coach feedback survey and identify whether a relationship existed between coach ratings of technique and active drag force-time profiles. Eight coaches were provided with a survey which included still images and video clips of thirty swimmers. Coaches were asked to rate technique on a simplified Likert scale. The coach ratings were then correlated against force data at the same time points. Findings revealed a range of low to moderate internal consistencies between coach ratings in all swimmers, thus indicating a major limitation of using the coach feedback survey in its current form. Alternatively, these low consistencies were maybe a direct result of coaches not being able to quantitatively assess swim technique as the norm is to assess qualitatively whilst on pool deck. The results found in this study should be interpreted with caution as only weak correlations were found between coach ratings and force-time profiles. Four main additions to the area of swimming biomechanics were concluded from this thesis: 1) the ATM protocol is a reliable tool to capture kinetic information for the assessment of free swimming; 2) a consistent increase was observed in stroke length and stroke rate between free swim and assisted towed trials which could enable the transfer of technical assumptions from assisted tow trial outputs to free swimming; 3) the ATM active drag forcetime profiles revealed the possibility of an optimal profile being established within the elite sprint swimmers thus enabling the ATM to be used in the future as an objective assessment of technique; and 4) a novel tool was presented which has potential to quantify technique proficiency with further investigation. iv

4 Table of Contents ABSTRACT... III STATEMENT OF AUTHORSHIP... V TABLE OF CONTENTS... VII LIST OF FIGURES... XIII LIST OF TABLES... XV LIST OF EQUATIONS... XVII LIST OF ABBREVIATIONS... XIX ACKNOWLEDGEMENTS... XXI PUBLICATIONS FROM DOCTORAL THESIS... XXV CHAPTER Introduction... 3 Background... 3 Statement of Problem... 6 Literature Review:... 6 Study 1:... 7 Study 2:... 7 Study 3:... 8 Study 4:... 9 Delimitations Limitations References vii

5 CHAPTER Literature Review Introduction Active Drag and Swim Performance Mechanical Power Output in Swimming Techniques of Drag Assessment Energetics Approach Numerical Simulations Experimental Techniques Measuring Active Drag System Velocity Perturbation Method Assisted Towing Method Review Summary References CHAPTER Study 1: Reliability of Active Drag Values Using the Assisted Towing Method Introduction Methods Participants Testing Protocols Data Processing Statistical Analysis Results viii

6 Discussion Conclusion References CHAPTER Study 2: A Comparison of Front Crawl Stroke Mechanics between Free Swim and Assisted Towed Swimming Introduction Method Results Discussion Conclusion References CHAPTER Study 3: Investigation of Front Crawl Stroke Phases within Active Drag Force-Time Profiles in Elite and Sub-Elite Sprint Swimmers Introduction Method Results Discussion Conclusion References ix

7 CHAPTER Study 4: Investigation of Coach Ratings of Technique and Active Drag Force-Time Profiles in Elite and Sub-Elite Front Crawl Sprint Swimmers Introduction Method Results Discussion Conclusion References CHAPTER Summary, Conclusions and Future Directions Summary Conclusions Study Study Study Study Future Directions APPENDIX A: PUBLICATIONS FROM DOCTORAL THESIS APPENDIX B: PUBLISHED LITERATURE REVIEW APPENDIX C: 2014 PROCEEDINGS FROM 32 ND ISBS, TENNESSEE, UNITED STATES APPENDIX D: 2014 PROCEEDINGS FROM 12 TH BIOMECHANICS AND MEDICINE IN SWIMMING, CANBERRA, AUSTRALIA x

8 APPENDIX E: 2013 PROCEEDINGS FROM THE ASICS CONFERENCE OF SCIENCE AND MEDICINE IN SPORT, PHUKET, THAILAND APPENDIX F: 2012 PROCEEDINGS FROM THE 30 TH ISBS, MELBOURNE, AUSTRALIA APPENDIX G: RIGHT AND LEFT SINGLE STROKE ACTIVE DRAG FORCE- TIME PROFILES AS USED IN STUDY APPENDIX H: COACH FEEDBACK SURVEYS APPENDIX I: RIGHT AND LEFT COACH EVENT RATINGS AND ACTIVE DRAG EVENT VALUES AS USED IN STUDY APPENDIX J: CONSENT FORMS AND PARTICIPANT INFORMATION xi

9 List of Figures Figure 2.1: Adapted experimental setup of drag collection from Di Prampero et al Figure 2.2: MAD-System setup for drag collection adapted from Hollander et al Figure 2.3: Modification of the VPM approach as utilised in, and adapted from Wang et al Figure 2.4: ATM technique to drag collection as shown in Sacilotto et al Figure 3.1: Assisted towing method set up 48 Figure 3.2: Placement of Velcro belt used in assisted tow trials 48 Figure 3.3: Example of the grip required to hold towing rope in passive tow trials.. 50 Figure 3.4: Example of a processed data output for a fluctuating tow trial.52 Figure 3.5: Example of a processed data output for a constant tow trial.53 Figure 3.6: Result summary of test retest reliability: a. Fluctuating trials: ICC = 0.94 (CI L = CI U = 0.97); b. Constant trials: ICC = 0.83 (CI L = 0.57, CI U = 0.94). = trials 1 and 2; = trials 1 and Figure 4.1: Example of a mixed image used to calculate assisted towed swim stroke rates..67 xiii

10 Figure 4.2: Ratio (stroke length/stroke rate) comparison with line of best fit between assisted towed swim and free swims stroke mechanics (r = 0.95) Figure 5.1: Male elite (a) and sub-elite (b) breakdown of stroke phases within an active drag profile in one-stroke cycle (right hand entry to subsequent right hand entry) Figure 5.2: Female elite (a) and sub-elite (b) breakdown of stroke phases within an active drag profile in one-stroke cycle (right hand entry to subsequent right hand entry).. 84 Figure 6.1: An example of a coach feedback survey question at a stroke event Figure 6.2: Time-code matching with active drag force data (Time-code rounded to the nearest of a second) xiv

11 List of Tables Table 3.1: Total sample mean (± SD) data for swim velocity, tow velocity, active drag, FINA point score and 100 m performance time. 55 Table 3.2: Intra-class correlations coefficients between different groups of trials and the average of all five trials within both constant and fluctuating active drag tow velocity trials Table 3.3: Intra-class correlation confidence limits between different groups of trials and the average of all five trials within both constant and fluctuating active drag tow velocity trials Table 3.4: Summary of within-subject variation shown in percentages presented as coefficients with 95 % confidence intervals 56 Table 4.1: Summary of differences between free swim and assisted tow trial variables Table 4.2: Significance between stroke mechanics and swim velocities in both free swim and assisted towed swimming Table 5.1: Summary of performance variables shown as mean ± SD Table 5.2: Percentage of time spent in each stroke phase during assisted towed swimming shown as mean ± SD percentages (%) xv

12 Table 5.3: Maximum and minimum active drag forces for an individual stroke cycle shown as mean ± SD Table 5.4: Time of maximum and minimum active drag forces, as a percentage of total stroke time shown as mean ± SD Table 6.1: Mean (± SD) of trial active drag and overall coach ratings 100 Table 6.2: Qualitative summary of common points at each stroke event made by all eight coaches Table 6.3: Trial active drag value correlation assessments between FINA, swim velocity, tow velocity and coach overall values for elite and sub-elite groups. 101 Table 6.4: Overall coach rating correlation assessments between FINA, swim velocity, tow velocity and trial active drag values for elite and sub-elite groups Table 6.5: Summary of mean coach event ratings and mean active drag event (D AE ) values Table 6.6: Elite correlation analysis between coach event ratings and FINA scores and active drag event values. 103 Table 6.7: Sub-elite correlation analysis between coach event ratings and FINA scores and active drag event values xvi

13 List of Equations Equation 2.1: Drag Force Equation 2.2: Mechanical Power Output Equation 2.3: Propelling Efficiency Equation 2.4: Active Drag Force (Toussaint et al. 48 ). 24 Equation 2.5: Active Drag Force (Kolmogorov and Duplishcheva 11 ) Equation 2.6: Active Drag Force (Alcock and Mason 27 ) Equation 2.7: Propulsion using ATM protocol (Mason et al. 54 ) 31 Equation 3.1: Active Drag Force (Alcock and Mason 2 ) Equation 4.1: Swim Velocity xvii

14 List of Abbreviations 3D A AIS ANOVA ATM C D CFD CI CI U CI L CV CV TE % D D A D AE D b D F F b FINA FS ICC Three Dimensional Frontal Surface Area Australian Institute of Sport Analysis of Variance Assisted Towing Method Drag Coefficient Computational Fluid Dynamics Confidence Intervals Confidence Intervals Upper Confidence Intervals Lower Coefficient of Variation Typical Error Coefficient of Variation Percentage Derivative Swimming Drag Active Drag Active Drag Event Drag Force with added resistance Drag Force Drag Force with added assistance The Federation Internationale de Natation Amateur Free Swimming Interclass Correlations xix

15 IdC K MAD-System m m/s N ɳ P P ρ PB P d P o SD SL SR TE TS v v 1 v 2 v b VO 2net VPM Index of Coordination Constant value Measuring Active Drag System Mass metres per second Newtons Propelling efficiency Propulsion Density of fluid Personal Best Useful Power Mechanical Power Output Standard Deviation Stroke Length Stroke Rate Typical Error Towed Swimming Swim Velocity Swim Velocity Assisted Swim Velocity Resisted Swim Velocity Net Maximal Oxygen Consumption Velocity Perturbation Method xx

16 Acknowledgements The support and guidance of many people enabled the completion of this body of work. The following is an attempt to show my gratitude and appreciation for all involved in my making this PhD possible. Firstly, to my mentor and supervisor in the field of swimming biomechanics, Dr Bruce Mason, without your guidance and wisdom, this journey would not have been a successful one! Sincere and genuine thanks are due and I have appreciated the opportunity to learn and work alongside one of the world s best. Sincere gratitude is due to Dr Nick Ball for your academic supervision over the last three and a half years! Our hot chocolate meetings were where these study designs, testing protocols, and final conclusions came to life. Thank you for allowing my creativeness to come forward through my work as well as tolerating my other thinking brain! Considerable acknowledgment is also due to Dr Peter Clothier, you were there right at the beginning of my biomechanics journey and I thank you for honing my scientific skills and being a sounding board for me, particularly in the latter stages of this work. To the staff of the Aquatic Testing, Training and Research Unit, at the Australian Institute of Sport, I thank you immensely. To Dr David Pease, thank you for always having the time for a quick chat, I appreciate the time you did give to me. To the post-graduate scholars over the years James Critoph, Cecilia Nguyen, Nicholas Smith, Renata Franco, Allison Higgs and Rebecca Pahl you have all helped me in some form or another over the years collecting data or listening to me sort through my ideas. I sincerely thank you for your xxi

17 assistance and patience. Renata, I will always cherish your friendship through what turned into a pinnacle year both personally and professionally. In particularly, staying up and helping me re-number reference lists! To Pendar Hazrati, thank you for helping with testing protocols and working out processing issues! Good luck on the completion of your own work! I am deeply indebted to the Australian Institute of Sport who enabled me access to their amazing facilities and scientists. The technology pool is easily the best in the world and being able to use this facility for testing made sessions run smoothly. Because of this resource, a more comprehensive data set was able to be collected. Sincere appreciation is due to Col McKintosh and Leon Williams. Col, thank you for the hours upon hours you helped Bruce and I work through the software required for collecting data and thank you for coming up with new ways to present our findings. Leon, thank you for all the time you spent with me working on the dyno any problem we had, even if it wasn t your speciality area I could always count on Leon coming over to the pool with his toolbox to help in any way he could! I would like to extend my gratitude to the University of Canberra, Faculty of Health Science for providing me the opportunity to pursue a Doctoral degree. The Research Student Office has a brilliant programme which offers extensive resources enabling the successful completion of this degree. From the writing workshops to the financial aid, I have enjoyed being a part of the UC research community and would like to extend my utmost appreciation. Appreciation is also due to the University of Western Sydney, particularly the School of Science and Health biostatistician Paul Faye for his assistance with analysis. xxii

18 I wish to express thanks to Andrew Dingley who was a great friend in the early days of learning and understanding the basic concepts of active drag and who was great to bounce ideas off. To all the coaches and swimmers who were a part of my testing I am sincerely grateful for your time and efforts. In particular Haydn Belshaw (for being the person I ve always spoken about swimming too), Brett Winkworth, Greg McWhirter, Coleman Wong, Matt Brown, Steve Critoph, Cameron McDonald, Yuriy Vdovychenko and Scott Talbot. I would also like to acknowledge the swimmers from Lane Cove Swim Club, Trinity Grammar Swim Club, Cherrybrook Carlile, Macquarie University Swim Club, Sydney University Swim Club, Ginninderra Swim Club, Woden Swim Club, AIS Swim Programme, and Marion Swim Club for the involvement within the studies. To my good friend Andrew who supported me in taking on this journey. Thank you for encouraging me and listening to me whilst I worked through my ideas. To my many other friends (Sydney, Canberra and swimming) who helped me through this stage in my life I am truly grateful for your love and support. To Ben, thank you for motivating me in the final stages of my work, I really appreciate your understanding, patience and reassurance! Finally, to my parents Lynelle and Marc Sacilotto thank you for allowing me to pursue my goals. Without your love and support I would not be the person I am today or working towards a career that I am passionate about. Thank you from the bottom of my heart! Thank you also to my brother William for - sometimes - taking an interest and listening to my work stories! I love you all. xxiii

19 Publications from Doctoral Thesis Sacilotto GB, Ball N, & Mason BR. A Biomechanical Review of the Techniques Used to Estimate or Measure Resistive Forces in Swimming. Journal of applied biomechanics. 2014;30: Sacilotto GB, Mason BR, Ball N, & Clothier PJ. Investigation of coach ratings of technique and force-time profiles in elite male front crawl sprint swimmers. In: Proceedings for the 32 nd International Society of Biomechanics in Sport; Jul 12-16, 2014; Tennessee, United States. Sacilotto GB, Clothier PJ, Mason BR, & Ball N. (2014) Variability in coach assessments of technique in front crawl sprint swimming. In: Proceedings for the 12 th International Symposium on Biomechanics and Medicine in Swimming; Apr 28-May 2, 2014; Canberra, Australia. p Sacilotto GB, Franco R, Mason BR, & Ball N. Investigation of front crawl stroke phases within force-time profiles in elite and sub-elite male sprint swimmers. Journal of Science and Medicine in Sport. 2013;16(Supp 1). Sacilotto GB, Mason BR, & Ball N. Intra-reliability of active drag values using the assisted towing method (ATM) approach. In: Proceedings for the 30 th International Society of Biomechanics in Sport; Jul 2-6, 2012; Melbourne, Australia. xxv