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Posture-movement changes following repetitive motion-induced shoulder muscle fatigue

J Electromyogr Kinesiol. 2009 Dec;19(6):1043-52. doi: 10.1016/j.jelekin.2008.10.009. Epub 2008 Dec 16.

Abstract

Repetitive motion-induced fatigue not only alters local motion characteristics but also provokes global reorganization of movement. However, the three-dimensional (3D) characteristics of these reorganization patterns have never been documented in detail. The goal of this study was to assess the effects of repetitive reaching-induced arm fatigue on the whole-body, 3D biomechanical task characteristics. Healthy subjects (N=14) stood and performed a continuous reaching task (RRT) between two targets placed at shoulder height to fatigue. Whole-body kinematic (Vicon), kinetic (AMTI force platforms) and electromyographic (EMG, Noraxon) characteristics were recorded. Maximal voluntary isometric efforts (MVIE) of the shoulder and elbow were measured pre- and post-RRT. Post-RRT shoulder elevation MVIE was reduced by 4.9+/-8.3% and trapezius EMG amplitude recorded during the RRT increased by 46.9+/-49.9% from the first to last minute of the RRT, indicating that arm fatigue was effectively induced. During fatigued reaching, subjects elevated their shoulder (11.7+/-10.5 mm) and decreased their average shoulder abduction angle by 8.3+/-4.4 degrees. These changes were accompanied by a lateral shift of the body's center of mass towards the non-reaching arm. These findings suggest a compensatory strategy to decrease the load on the fatigued shoulder musculature.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Physiological / physiology
  • Adult
  • Arm / physiology
  • Female
  • Humans
  • Male
  • Movement / physiology*
  • Muscle Contraction / physiology*
  • Muscle Fatigue / physiology*
  • Muscle, Skeletal / physiology*
  • Physical Exertion / physiology
  • Postural Balance / physiology*
  • Posture / physiology*
  • Psychomotor Performance / physiology
  • Range of Motion, Articular / physiology*
  • Shoulder Joint / physiology*