MECHANICAL MUSCLE PROPERTIES AND INTERMUSCULAR COORDINATION IN MAXIMAL AND SUBMAXIMAL CYCLING: THEORETICAL AND PRACTICAL IMPLICATIONS A thesis submitted for the degree of Doctor of Philosophy By Paul Richard Barratt School of Sport and Education Brunel University March 2014 This thesis is dedicated to my wife Emily for her love, support, understanding, encouragement and assistance 2 ABSTRACT The ability of an individual to perform a functional movement is determined by a range of mechanical properties including the force and power producing capabilities of muscle, and the interplay of force and power outputs between different muscle groups (intermuscular coordination). Cycling presents an ideal experimental model to investigate these factors as it is an ecologically valid multi-joint movement in which kinematics and resistances can be tightly controlled. The overall goal of this thesis was thereby to investigate mechanical muscle properties and intermuscular coordination during maximal and submaximal cycling. The specific research objectives were (a) to determine the contribution of these factors to maximal and submaximal cycling, and (b) to determine the extent to which these factors set the limit of performance in maximal cycling. The contribution of mechanical muscle properties and intermuscular coordination were investigated by observing joint kinetics and joint kinematics across variations in crank lengths and pedalling rates during maximal and submaximal cycling. The extent to which these factors set the limit of performance in maximal cycling was assessed by observing joint-level kinetics of world-class track sprint cyclists. The findings of this investigation formed the rationale for the fourth study which used an ankle brace intervention to investigate the effects of a fixed ankle on joint biomechanics and performance during maximal cycling. Sophisticated intermuscular coordination strategies were observed in both submaximal and maximal cycling, supporting the generalised notion that high levels of intermuscular coordination are required to perform functional multi-joint movement tasks. Furthermore, it was found that the maximal cycling task is governed by the interaction of the force-velocity relationship and excitation-relaxation kinetics, suggesting that task-specific mechanical muscle properties are the dominant contributing factor in maximal movements. In terms of the extent to which these factors limit performance in maximal cycling, it was demonstrated that world-class track sprint cycling performance is governed by the ability to generate higher joint moments at the ankle and knee, and that these joint moments are facilitated by enhanced muscular strength about these joints. These findings allow us to speculate that the limits of performance in maximal human movements lie in extraordinary muscular strength in task-specific joint actions. These findings give an insight into the mechanisms that underpin maximal and submaximal cycling, and provide a theoretical framework with which to understand sprint cycling performance. This knowledge has significant applied relevance for athletes and coaches seeking to improve sprint cycling performance. 3 ACKNOWLEDGEMENTS I gratefully acknowledge the contribution of the following people: Dr. Thomas Korff without whose expertise, dedication and guidance this thesis would not have been possible. Professor Jim Martin for allowing me to use his lab (and expertise) for the first two studies, and in the process becoming the best PhD mentor I could have hoped for. The World-Class Cyclists and Coaches of the Great Britain Cycling Team who gave up their valuable training time to take part in these studies and in the process develop our understanding of cycling performance. The local cyclists from Utah and Manchester who enthusiastically took part in a range of novel cycling tasks. Simon Powers for helping to recruit the best sub-elite cyclists British Cycling has to offer. Julie Bradshaw for saving my bacon on more occasions than I care to admit. Dr. Scott Gardner for sparking my interest in “real” biomechanics, and for teaching me how to apply it in the real world. The Engineering and Physical Sciences Research Council for financial support for my studies. The English Institute of Sport for financial support for my studies. My wife Emily for her tolerance and patience of having to share weekends and evenings with this thesis. 4 CONTENTS Page Number Chapter 1: General Introduction…………………………………………….. 12 An Introduction to Pedalling Mechanics and Associated Mechanisms…………….. 16 General Overview……………………………………………………………………….. 16 The Interaction of Mechanical Muscle Properties and Intermuscular Coordination…… 17 Definitions………………………………………………………………………………. 19 Chapter 2: Literature Review: Joint-Level Analyses of Mechanical Output in Cycling……………………………………………………………… 23 Joint-Level Analyses of Mechanical Output in Submaximal Cycling……………… 24 General Observations…………………………………………………………………… 24 Mechanical Muscle Properties………………………………………………………….. 25 Intermuscular Coordination……………………………………………………………... 27 Joint-Level Analyses of Mechanical Output in Maximal Cycling………………….. 28 General Observations. ………………………………………………………………….. 28 Mechanical Muscle Properties………………………………………………………….. 29 Intermuscular Coordination……………………………………………………………... 31 Joint-Level Analyses of Mechanical Output in Elite Sprint Athletes…………………... 32 Summary………………………………………………………………………………… 33 Chapter 3: Changes in Joint Kinetics across Crank Lengths and Pedalling Rates During Maximal Cycling……………………………………………………. 36 Introduction……………………………………………………………………………... 36 Methods…………………………………………………………………………………. 38 Results…………………………………………………………………………………... 42 Discussion……………………………………………………………………………….. 47 Chapter 4: Changes in Joint Kinetics across Crank Lengths and Pedal Speeds During Submaximal Cycling…………………………………………. 51 Introduction……………………………………………………………………………... 51 Methods…………………………………………………………………………………. 53 Results…………………………………………………………………………………... 58 Discussion……………………………………………………………………………….. 63 Chapter 5: Biomechanical Factors Associated with World-Class Track Sprint Cycling Performance………………………………………………….. 68 Introduction……………………………………………………………………………... 68 Methods…………………………………………………………………………………. 70 Results…………………………………………………………………………………... 74 Discussion……………………………………………………………………………….. 78 Chapter 6: The Effect of a Rigid Ankle on Joint Biomechanics and Performance in Maximal Cycling………………………………………………… 83 Introduction……………………………………………………………………………... 83 Methods…………………………………………………………………………………. 84 Results…………………………………………………………………………………... 89 Discussion……………………………………………………………………………….. 94 5 Chapter 7: General Discussion…………………………………………………….. 100 Objective 1………………………………………………………………………………. 101 Main Findings…………………………………………………………………………… 101 Implications……………………………………………………………………………... 102 Objective 2………………………………………………………………………………. 103 Main Findings…………………………………………………………………………… 103 Implications……………………………………………………………………………... 103 Limitations………………………………………………………………………………. 105 Future Directions………………………………………………………………………... 106 Summary………………………………………………………………………... 107 Chapter 8: References………………………………………………………………. 109 Chapter 9: Appendix………………………………………………………………... 120 Selection of Filter Cut-Off Frequencies………………………………………………… 120 Prediction of Errors due to the Underestimation of Leg Mass in World-Class Track Sprint Cyclists…………………………………………………………………………... 123 Research Ethics Approval Letters………………………………………………………. 126 Published Journal Paper………………………………………………………………… 130 Conference Presentations……………………………………………………………….. 131 6 LIST OF TABLES Table 1. Power delivered to the right pedal during maximal cycling with variations in crank length and pedalling rate. Joint powers are averaged over complete pedal cycles and normalised to pedal power. Joint powers are presented as means and standard deviations on the main diagonal of each table. Effect sizes for pairwise comparisons are presented in the remaining cells. Table 2. Extension and flexion powers produced at the ankle, knee and hip. Powers are normalised to pedal power. Means and standard deviations are presented on the main diagonal of each table. Effect sizes for pairwise comparisons are presented in the remaining cells. Table 3. Joint angular velocities at the hip, knee and ankle. Means and standard deviations are presented on the main diagonal of each table. Effect sizes for pairwise comparisons are presented in the remaining cells. Table 4. Joint excursions at the hip, knee and ankle. Means and standard deviations are presented on the main diagonal of each table. Effect sizes for pairwise comparisons are presented in the remaining cells. Table 5. Crank lengths, pedalling rates and pedal speeds used in both experimental conditions. The constant pedal speed condition was included to test whether crank length per se would have a confounding effect on any of the dependent variables. Table 6. Details of the statistical analyses in the constant pedalling rate and constant pedal speed conditions. In the constant pedalling rate condition increases in pedal speed caused large increases extension and flexion velocities at the knee and hip, and moderate decreases in knee extension moment. Table 7. Joint angular velocities at the ankle, knee and hip. Means and standard deviations are presented on the main diagonal of each table. Effect sizes for pairwise comparisons are presented in the remaining cells. Table 8. Joint extension and flexion moments at the ankle, knee and hip. Means and standard deviations