• Maarten Bobbert
Keywords: human, model, explosive movements, control, simulation, optimization


The purpose of this study was to gain a better understanding of why coordination, or the timing of muscle actions, affects performance in vertical jumping. A forward dynamic simulation model was used, which calculated the motion corresponding to stimulationtime input to the muscles. A maximum-height jump was found by optimizing the stimulation-time input. Jump height amounted to 41 cm. Subsequently, the solution space was constrained by demanding that soleus was switched on 100 ms before any of the other muscles, and the stimulation-time input was again optimized. Jump height in the constrained jump was 9 cm less than that in the maximum-height jump, primarily because glutei and hamstrings produced less work. In the constrained jump, the glutei dissipated energy early in the push-off, and during shortening they produced less energy because their shortening velocity increased too quickly. These undesired effects could be explained by the effects of premature rotation of the foot on the motion in the hip joint. The analysis presented in this paper shows by which mechanisms the timing of muscle actions affects performance in vertical jumping.