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The collisional geometry of economical walking predicts human leg and foot segment proportions

Usherwood, JR

Authors

JR Usherwood



Abstract

Human walking appears complicated, with many muscles and joints performing rapidly varying roles over the stride. However, the function of walking is simple: to support body weight as it translates economically. Here, a scenario is proposed for the sequence of joint and muscle actions that achieves this function, with the timing of muscle loading and unloading driven by simple changes in geometry over stance. In the scenario, joints of the legs and feet are sequentially locked, resulting in a vaulting stance phase and three or five rapid 'mini-vaults' over a series of 'virtual legs' during the step-to-step transition. Collision mechanics indicate that the mechanical work demand is minimized if the changes in the centre-of-mass trajectory over the step-to-step transition are evenly spaced, predicting an even spacing of the virtual legs. The scenario provides a simple account for the work-minimizing mechanisms of joints and muscles in walking, and collision geometry allows leg and foot proportions to be predicted, accounting for the location of the knee halfway down the leg, and the relatively stiff, plantigrade, asymmetric, short-toed human foot.

Citation

Usherwood, J. (2023). The collisional geometry of economical walking predicts human leg and foot segment proportions. Journal of the Royal Society, Interface, 20(200), https://doi.org/10.1098/rsif.2022.0800

Journal Article Type Article
Acceptance Date Mar 3, 2023
Publication Date 2023
Deposit Date Jun 19, 2024
Publicly Available Date Jun 19, 2024
Print ISSN 1742-5689
Publisher The Royal Society
Peer Reviewed Peer Reviewed
Volume 20
Issue 200
DOI https://doi.org/10.1098/rsif.2022.0800
Keywords gait; leg; walk; knee; ankle; toe; MUSCLE CONTRIBUTIONS; DYNAMIC SIMULATIONS; SUPPORT; OPTIMIZATION; EVOLUTION; MODEL; GAITS; PROGRESSION; LOCOMOTION; BEHAVIOR

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