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Author Notes:

Correspondence: Lena H. Ting, Tel: +1 404-894-5216; Fax: +1 404-385-5044; Email: lting@emory.edu

Acknowledgments: The authors acknowledge and thank Lale Korkmaz for conversion of the musculoskeletal model to SIMM, Keith van Antwerp for assistance with the muscle models, and Jane Macpherson for the postural response data.

Subject:

Research Funding:

Support provided by NIH HD46922.

Keywords:

  • Musculoskeletal model
  • Endpoint force
  • Balance
  • Feasible force set

Biomechanical capabilities influence postural control strategies in the cat hindlimb

Tools:

Journal Title:

Journal of Biomechanics

Volume:

Volume 40, Number 10

Publisher:

, Pages 2254-2260

Type of Work:

Article | Post-print: After Peer Review

Abstract:

During postural responses to perturbations, horizontal plane forces generated by the cat hindlimb are stereotypically directed either towards or away from the animal’s center of mass, independent of perturbation direction. We used a static, three-dimensional musculoskeletal model of the hindlimb to investigate possible biomechanical determinants of this “force constraint strategy” (Macpherson, 1988). We hypothesized that directions in which the hindlimb can produce large forces are preferentially used in postural control. We computed feasible force sets (FFS) based on hindlimb configurations of three cats during postural equilibrium tasks (Jacobs and Macpherson, 1996) and compared them to horizontal plane postural force directions. The grand mean FFS was bimodal, with maxima near the posterior-anterior axis (−86±8° and 71±4°), and minima near the medial-lateral axis (177±8° and 8±8°). Postural force directions clustered near both maxima; there were no medial postural forces near the absolute minimum. However, the medians of the anterior and posterior postural force direction histograms in the right hindlimb were rotated counter-clockwise from the FFS maxima (p<0.05; Wilcoxon signed-rank test). Because the posterior-anterior alignment of the FFS is consistent with a hindlimb structure optimized for locomotion, we conclude that the biomechanical capabilities of the hindlimb strongly influence, but do not uniquely determine the force directions observed in the force constraint strategy. Forces used in postural control may reflect a balance between a neural preference for using forces in the directions of large feasible forces and other criteria, such as the stabilization of the center of mass, and muscular coordination strategies.

Copyright information:

© 2006 Elsevier Ltd. All rights reserved.

This is an Open Access work distributed under the terms of the Creative Commons Attribution-NonCommerical-NoDerivs 3.0 Unported License (http://creativecommons.org/licenses/by-nc-nd/3.0/).

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