Learning effects on muscle modes and multi-mode postural synergies.

Full Abstract

We used the framework of the uncontrolled manifold hypothesis to explore the effects of practice on the composition of muscle groups (M-modes) and multi-M-mode synergies stabilizing the location of the center of pressure (COP). In particular, we tested a hypothesis that practice could lead to a transition from co-contraction muscle activation patterns to reciprocal patterns. We also tested a hypothesis that new sets of M-modes would form stronger synergies stabilizing COP location. Subjects practiced load release tasks for five days while standing on a board with a narrow support surface (unstable board). Their M-modes and indices of multi-M-mode synergies were computed during standing without instability and during standing on an unstable board before practice, in the middle of practice, and at the end of practice. During standing without instability, subjects showed two consistent M-modes uniting dorsal and ventral muscles of the body respectively (reciprocal modes). While standing on an unstable board, prior to practice, subjects commonly showed M-modes uniting muscle pairs with opposing actions at major leg joints-co-contraction modes. Such sets of M-modes failed to stabilize the COP location in the anterior-posterior direction. Practice led to better task performance reflected in fewer incidences of lost balance. This was accompanied by a drop in the occurrence of co-contraction M-modes and the emergence of multi-mode synergies stabilizing the COP location. We conclude that the central nervous system uses flexible sets of elemental variables (modes) to ensure stable trajectories of important performance variables (such as COP location). Practice can lead to adjustments in both the composition of M-modes and M-mode co-variation patterns resulting in stronger synergies stabilizing COP location.

Author information

Author/s: Asaka, Tadayoshi (T); Wang, Yun (Y); Fukushima, Junko (J); Latash, Mark L (ML);

Affiliation: Department of Health Sciences, School of Medicine, Hokkaido University, Hokkaido, Japan.

Grants: NS-035032 (Agency:NINDS NIH HHS) ; R01 NS035032-11 (Agency:NINDS NIH HHS)

Journal and publication information

Publication Type: Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't

Journal: Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale (Exp Brain Res), published in Germany. (Language: eng)

Reference: 2008-Jan; vol 184 (issue 3) : pp 323-38

Dates: Created 2007/12/14; Completed 2008/05/14; Revised 2009/01/05;

PMID: 17724582, status: MEDLINE (last retrieval date: 2/18/2009, IMS Date: )

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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