Changes in movement variability and task performance during a fatiguing repetitive pointing task |
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| Institution: | 1. Department of Kinesiology and Physical Education, McGill University, Montreal, QC H2W 1S4, Canada;2. Occupational Biomechanics and Ergonomics Laboratory, Michael Feil and Ted Oberfeld/CRIR Research Centre, Jewish Rehabilitation Hospital, Laval, QC H7V 1R2, Canada;3. Laboratoire de simulation et modélisation du mouvement, Département de kinésiologie, Université de Montréal, Laval, QC H7N 0A5, Canada;4. Grado Department of Industrial and Systems Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA;1. Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, University of Gävle, Sweden;2. Department of Community Medicine and Rehabilitation, Umeå University, Umeå, Sweden;1. Laboratory of Clinical and Occupational Kinesiology (LACO), Department of Physical Therapy, Federal University of São Carlos, Rodovia Washington Luís, km 235 – SP-310, São Carlos, São Paulo, Brazil;2. Department of Kinesiology and Physical Education, McGill University, 475 Pine Avenue West, Montreal, Quebec H2W 1S4, Canada;3. Laboratory for Ergonomics and Work-related Disorders, Sport Sciences, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7 D-3, 9220 Aalborg East, Denmark |
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| Abstract: | Changes in neuromuscular strategies employed with fatigue during multi-joint movements are still poorly understood. Studies have shown that motor variability of individual joints increases when performing upper limb tasks to fatigue, while movement parameters related to the task goal remain constant. However, how the inter-limb coordination and its variability change during specific movement phases with fatigue is still unclear. The aim of this study was to assess the effects of neck-shoulder fatigue on shoulder and elbow kinematic variabilities, shoulder-elbow coordination and its variability, and endpoint characteristics during different phases of a forward pointing movement. Nineteen healthy young adults continuously performed a repetitive pointing task until fatigue (Borg rating of 8/10). Changes in elbow-shoulder coordination through the movement were assessed using the continuous relative phase and statistical nonparametric mapping methods. At the end of the task, muscle fatigue was evidenced by significant increases in anterior deltoid (+13%) and biceps brachii (+30%) activity. Shoulder horizontal abduction, elbow flexion variability and shoulder-elbow coordination variability were increased with fatigue at different moments of the movement cycle (shoulder: during the first 17% and most of the second half movement, elbow: from 73% to 91%, coordination: almost the whole movement). However, movement timing errors and endpoint spatial variability were mostly preserved, even with fatigue. We showed that increased variability with fatigue is not only observed in the fatigued joint (shoulder), but also in the elbow and shoulder-elbow coordination, and may have a goal of preserving global task performance. |
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| Keywords: | Multi-joint Kinematics Coordination Relative phase |
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