Mechanical muscle properties and intermuscular coordination in maximal and submaximal cycling: theoretical and practical implications

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.