Muscle synergies during shifts of the center of pressure by standing persons: Identification of muscle modes

Vijaya Krishnamoorthy, Simon Goodman, Vladimir Zatsiorsky, Mark L. Latash

Research output: Contribution to journalArticle

130 Scopus citations

Abstract

When a standing person performs a movement such that the center of gravity shifts, the activity of postural muscles adjusts to keep the balance. We assume that such adjustments are controlled using a small set of central variables, while each variable induces changes in the activity of a subgroup of postural muscles. The purpose of this study has been to identify such muscle groups (muscle modes or M-modes) and compare them across tasks and subjects. Four tasks required the subjects to release a load from extended arms leading to a center of pressure (COP) shift prior to the load release. The fifth task required an explicit COP shift by voluntary sway. Electromyographic activity of 11 postural muscles on one side of the body was integrated over a 100-ms interval corresponding to the early stage of the COP shift, and this integrated EMG activity was subjected to a principal component (PC) analysis across multiple repetitions of each task. Three PCs were identified and associated with a "push-back M-mode," a "push-forward M-mode," and a "mixed M-mode." Cluster analysis of the PC vectors across tasks and across subjects confirmed the existence of distinctive push-forward and push-back muscle groups. PC vectors were also compared across tasks and across subjects using cosines as a measure of colinearity between pairs of vectors. In general, M-modes were similar across both tasks and subjects. We conclude that shifts of the COP, whether implicit or explicit, are controlled using a small set of central variables associated with changes in the activity of robust subsets of postural muscles. These results can be used for future analysis of muscle synergies associated with postural tasks.

Original languageEnglish (US)
Pages (from-to)152-161
Number of pages10
JournalBiological Cybernetics
Volume89
Issue number2
DOIs
StatePublished - Aug 2003

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Computer Science(all)

Fingerprint Dive into the research topics of 'Muscle synergies during shifts of the center of pressure by standing persons: Identification of muscle modes'. Together they form a unique fingerprint.

  • Cite this