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Keywords:

  • muscle cocontraction;
  • knee;
  • elbow;
  • motor control;
  • EMG

Abstract

Introduction: We examined generalized versus joint-specific influences on muscle co-activation.

Methods: Muscle co-activation was assessed during maximal isometric and isokinetic knee and elbow joint extension moments in 48 healthy subjects (27 men). Local (joint-specific) and generalized (person-specific) contributions were examined using a combination of statistical tests: regression using generalized estimating equations (GEEs), exploratory factor analysis, and cluster analysis.

Results: GEEs produced similar significant coefficients for gender and joint; contraction type and test condition (angle or velocity) were not significant. Factor analysis indicated 2 joint-based factors, and cluster analysis indicated 2 groups of individuals, those with or without elevated co-activation at the knee and elbow. Women exhibited greater co-activation at both joints, however, no consistent influences of angle or velocity were observed at either joint.

Discussion: We conclude that muscle co-activation is a neuromuscular control response determined by local, joint-specific, and generalized, individual-specific influences. © 2013 Wiley Periodicals, Inc.