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

Fuller, Jason R.; Lomond, Karen V.; Fung, Joyce; Côté, Julie N.

doi:10.1016/j.jelekin.2008.10.009

« Previous Next »Journal of Electromyography and Kinesiology
Volume 19, Issue 6 , Pages 1043-1052, December 2009

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

Jason R. Fuller
- Department of Kinesiology and Physical Education, McGill University, 475 Pine Avenue West, Montreal, Quebec, Canada H2W 1S4
- Jewish Rehabilitation Hospital, Research Site of CRIR, Laval, Quebec, Canada
- Corresponding author. Address: Department of Kinesiology and Physical Education, McGill University, 475 Pine Avenue West, Montreal, Quebec, Canada H2W 1S4. Tel.: +450 688 9550x4827.
Karen V. Lomond
- Department of Kinesiology and Physical Education, McGill University, 475 Pine Avenue West, Montreal, Quebec, Canada H2W 1S4
- Jewish Rehabilitation Hospital, Research Site of CRIR, Laval, Quebec, Canada
- Tel.: +450 688 9550x4827.
Joyce Fung
- Jewish Rehabilitation Hospital, Research Site of CRIR, Laval, Quebec, Canada
- School of Physical and Occupational Therapy, McGill University, 3654 Promenade Sir William Osler, Montreal, Quebec, Canada H3G 1Y5
- Tel.: +514 398 5734; fax: +514 398 8193.
Julie N. Côté
- Department of Kinesiology and Physical Education, McGill University, 475 Pine Avenue West, Montreal, Quebec, Canada H2W 1S4
- Jewish Rehabilitation Hospital, Research Site of CRIR, Laval, Quebec, Canada
- Tel.: +514 398 4184x0539.

Received 11 June 2008; received in revised form 13 October 2008; accepted 14 October 2008. published online 17 December 2008.

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±10.5mm) and decreased their average shoulder abduction angle by 8.3±4.4°. 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.