Adaptations to isolated shoulder fatigue during simulated repetitive work. Part II: Recovery |
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| Affiliation: | 1. Department of Kinesiology, McMaster University, Hamilton, Ont., Canada L8S 2K1;2. McMaster Integrative Neuroscience Discovery & Study (MiNDS), McMaster University, Hamilton, Ont., Canada L8S 2K1;1. Department of Industrial and Systems Engineering, Auburn University, 3301 Shelby Center for Engineering Technology, Auburn, AL 36849, USA;2. School of Forestry and Wildlife Sciences, Auburn University, 3423 School of Forestry and Wildlife Sciences, Auburn, AL 36849, USA;3. Department of Occupational and Environmental Health, University of Iowa, UI Research Park #164 IREH, Iowa City, IA 52242, USA;4. Department of Occupational and Environmental Health, University of Iowa, S347 CPHB, Iowa City, IA 52242, USA;1. University of Siegen, Department of Management Information Science, Kohlbettstraβe 15, D-57068 Siegen, Germany;2. ISAE-SUPAERO, Department of Complex Systems, Université de Toulouse, 10 avenue Edouard Belin, BP 54032, 31055 Toulouse Cedex 4, France;1. Centre for Musculoskeletal Research, Menzies Health Institute Queensland, Griffith University, Gold Coast, Australia;2. Department of Neurorehabilitation Engineering, University Medical Center Göttingen, Georg-August University, Göttingen, Germany;3. Department of Management and Engineering, University of Padua, Vicenza, Italy;4. Auckland Bioengineering Institute & Dept of Engineering Science, University of Auckland, Auckland, New Zealand;5. Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL, USA |
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| Abstract: | The shoulder allows kinematic and muscular changes to facilitate continued task performance during prolonged repetitive work. The purpose of this work was to examine changes during simulated repetitive work in response to a fatigue protocol. Participants performed 20 one-minute work cycles comprised of 4 shoulder centric tasks, a fatigue protocol, followed by 60 additional cycles. The fatigue protocol targeted the anterior deltoid and cycled between static and dynamic actions. EMG was collected from 14 upper extremity and back muscles and three-dimensional motion was captured during each work cycle. Participants completed post-fatigue work despite EMG manifestations of muscle fatigue, reduced flexion strength (by 28%), and increased perceived exertion (∼3 times). Throughout the post-fatigue work cycles, participants maintained performance via kinematic and muscular adaptations, such as reduced glenohumeral flexion and scapular rotation which were task specific and varied throughout the hour of simulated work. By the end of 60 post-fatigue work cycles, signs of fatigue persisted in the anterior deltoid and developed in the middle deltoid, yet perceived exertion and strength returned to pre-fatigue levels. Recovery from fatigue elicits changes in muscle activity and movement patterns that may not be perceived by the worker which has important implications for injury risk. |
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| Keywords: | Occupational Co-ordination Movement Kinematics EMG Control |
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