Variable gearing during locomotion in the human musculoskeletal system

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Science  29 Jul 1994:
Vol. 265, Issue 5172, pp. 651-653
DOI: 10.1126/science.8036513


Human feet and toes provide a mechanism for changing the gear ratio of the ankle extensor muscles during a running step. A variable gear ratio could enhance muscle performance during constant-speed running by applying a more effective prestretch during landing, while maintaining the muscles near the high-efficiency or high-power portion of the force-velocity curve during takeoff. Furthermore, during acceleration, variable gearing may allow muscle contractile properties to remain optimized despite rapid changes in running speed. Forceplate and kinematic analyses of running steps show low gear ratios at touchdown that increase throughout the contact phase.

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