The control of the arm's equilibrium position
File(s)takagi2024.pdf (1.38 MB)
Accepted version
Author(s)
Takagi, A
Burdet, E
Koike, Y
Type
Journal Article
Abstract
To generate a force, the brain activates muscles that act like springs to pull the arm toward a new equilibrium position. The equilibrium position (EP) is central to our understanding of the biological control of viscoelastic muscles. While there is evidence of the EP during the control of limb posture, EPs have not been directly identified when the limb exerts a force against the environment. Here, we asked participants to apply a constant force in one of eight directions against a point-like constraint. This constraint was released abruptly to observe the final position to which the arm converged. Importantly, the same force magnitude was maintained while changing the arm's stiffness by modulating the strength of the hand's power grasp. The final position moved further away from the constraint as the arm became less stiff and was inversely proportional to the arm's stiffness, thereby confirming that the final position was the arm's EP. These results demonstrate how the EP changes with the arm's stiffness to produce a desired force in different directions.
Date Issued
2024-04
Date Acceptance
2024-03-18
ISSN
0022-3077
Publisher
American Physiological Society
Start Page
750
End Page
756
Journal / Book Title
Journal of Neurophysiology
Volume
131
Issue
4
Copyright Statement
Copyright © 2024 the American Physiological Society. This is the author’s accepted manuscript made available under a CC-BY licence in accordance with Imperial’s Research Publications Open Access policy (www.imperial.ac.uk/oa-policy)
Identifier
https://journals.physiology.org/doi/epdf/10.1152/jn.00011.2024
https://www.ncbi.nlm.nih.gov/pubmed/38507295
Publication Status
Published
Coverage Spatial
United States
Date Publish Online
2024-04-15