Position-dependent torque coupling and associated muscle activation in the hemiparetic upper extremity

Michael D. Ellis, Ana Maria Acosta, Jun Yao, Julius P.A. Dewald*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

77 Scopus citations

Abstract

Previous studies have demonstrated abnormal joint torque coupling and associated muscle coactivations of the upper extremity in individuals with unilateral stroke. We investigated the effect of upper limb configuration on the expression of the well-documented patterns of shoulder abduction/elbow flexion and shoulder adduction/elbow extension. Maximal isometric shoulder and elbow torques were measured in stroke subjects in four different arm configurations. Additionally, an isometric combined torque task was completed where subjects were required to maintain various levels of shoulder abduction/adduction torque while attempting to maximize elbow flexion or extension torque. The dominant abduction/elbow flexion pattern was insensitive to changes in limb configuration while the elbow extension component of the adduction/extension pattern changed to elbow flexion at smaller shoulder abduction angles. This effect was not present in control subjects without stroke. The reversal of the torque-coupling pattern could not be explained by mechanical factors such as muscle length changes or muscle strength imbalances across the elbow joint. Potential neural mechanisms underlying the sensitivity of the adduction/elbow extension pattern to different somatosensory input resultant from changes in limb configuration are discussed along with the implications for future research.

Original languageEnglish (US)
Pages (from-to)594-602
Number of pages9
JournalExperimental Brain Research
Volume176
Issue number4
DOIs
StatePublished - Feb 2007

Keywords

  • Arm
  • Electromyography
  • Posture
  • Stroke
  • Torque

ASJC Scopus subject areas

  • Neuroscience(all)

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