A Procedure to Determine Equilibrium Postural Configurations for Arbitrary Locations of the Feet

[+] Author and Article Information
L. J. Gonzalez, S. V. Sreenivasan

Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX 78712

J. L. Jensen

Department of Kinesiology & Health Education, The University of Texas at Austin, Austin, TX 78712

J Biomech Eng 121(6), 644-649 (Dec 01, 1999) (6 pages) doi:10.1115/1.2800867 History: Received May 12, 1998; Revised July 21, 1999; Online October 30, 2007


This research was directed toward predicting postural equilibrium configurations in normal humans for asymmetric locations of the feet. The objective of the study was to identify trends in the variation of the location of ground center of pressure (COP) with increasing levels of asymmetry in the foot placement. The procedure developed here minimized the muscular effort (active torques) in the lower extremities while maximizing postural stability margins for given foot locations. Minimizing muscular effort led to fully extended knees, and maximal stability margin led to the COP moving toward the rear foot in asymmetric stance. A combined analytical-numerical optimization scheme was used to avoid singularities that can arise due to the fact that at equilibrium postural configurations, the torso lies at or near the workspace boundary of the lower extremities. Experiments were conducted and the results obtained were in keeping with the model predictions. This basic understanding of asymmetric stance is important for studying asymmetric postural mechanics in the presence of external disturbances, and for extending the results from normal subjects to humans at both ends of the life span.

Copyright © 1999 by The American Society of Mechanical Engineers
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