A gravitational impulse model predicts collision impulse and mechanical work during a step-to-step transition

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The simplest walking model, which assumes an instantaneous collision with negligible gravity effect, is limited in its representation of the collision mechanics of human gaits because the actual step-to-step transition occurs over a finite duration of time with finite impulsive ground reaction forces (GRFs) that have the same order of magnitude as the gravitational force. In this study, we propose a new collision model that includes the contribution of the gravitational impulse to the momentum change of the center of mass (COM) during a step-to-step transition. To validate the model, we measured the GRFs of six subjects' over-ground walking at five different gait speeds and calculated the collision impulses and mechanical work. The data showed a significant contribution of the gravitational impulse to the momentum change during collision. To compensate for the gravity, the magnitudes of collision impulse and COM work were estimated to be much greater than in previous predictions. Consistent with the model prediction, push-off propulsion fully compensated for the collision loss, implying the step-to-step transition occurred in an energetically optimal manner. The new model predicted a moderate change in the collision mechanics with gait speed, which seems to be physiologically achievable. The gravitational collision model enables us to better understand collision dynamics during a step-to-step transition. (C) 2010 Elsevier Ltd. All rights reserved.
Publisher
ELSEVIER SCI LTD
Issue Date
2011-01
Language
English
Article Type
Article
Keywords

SIMPLEST WALKING MODEL; CENTER-OF-MASS; RUN TRANSITION; TREADMILL; SPEED; COST; OPTIMIZATION; DETERMINANT; LOCOMOTION; ENERGETICS

Citation

JOURNAL OF BIOMECHANICS, v.44, no.1, pp.59 - 67

ISSN
0021-9290
DOI
10.1016/j.jbiomech.2010.08.024
URI
http://hdl.handle.net/10203/98694
Appears in Collection
ME-Journal Papers(저널논문)
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