Effects of shoulder rotation combined with elbow flexion on discomfort and EMG activity of ECRB muscle |
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| Affiliation: | 1. Department of Mechanical Engineering, Aligarh Muslim University, Aligarh, UP 202002, India;2. Ergonomics Research Division, Department of Mechanical Engineering, Aligarh Muslim University, Aligarh, UP 202002, India;1. Engineering & Control Technology Branch, National Institute for Occupational Safety and Health, Morgantown, WV 26505, USA;2. Biodynamics Laboratory, University of Connecticut Health Center, Farmington, CT 06030-2017, USA;1. Toronto Rehabilitation Institute, Toronto, ON, Canada;2. Depart of Mechanical and Aerospace Engineering, Carleton University, Ottawa, ON, Canada;3. Faculty of Kinesiology, University of New Brunswick, Fredericton, NB, Canada;4. School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John''s, NL, Canada;1. Agricultural Machinery Engineering Department, Shahr-e Kord University, Shahr-e Kord, Iran;2. Department of Ergonomics, Tabriz University of Medical Sciences, Tabriz 51666, Iran;1. The Institution of Textiles and Clothing, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong;1. Department of Design, Faculty of Architecture, Arts and Communication, UNESP-Univ Estadual Paulista, Bauru, SP, Brazil;2. Programme of Post Graduation in Design, UNESP-Univ Estadual Paulista, Bauru, SP, Brazil;3. Department of Mechanical Engineering, Sao Carlos School of Engineering, University of Sao Paulo, SP, Brazil;4. Department of Neuroscience and Behavioral Sciences, University of Sao Paulo, Ribeirao Preto, SP, Brazil;5. Programme of Post Graduation Interunits in Bioengineering, University of Sao Paulo, Sao Carlos, SP, Brazil |
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| Abstract: | Work related MusculoSkeletal Disorders (WMSDs) are injuries or dysfunctions caused by occupational or non occupational tasks involving bad postures, high frequency of exertions or high force levels. In the present study, the effects of shoulder flexion/extension combined with elbow flexion angle on discomfort score were investigated for repetitive gripping task. A laboratory experimental simulation was conducted. Ten male participants volunteered in this study. Four levels of shoulder flexion/extension (−45° extension, 0° neutral, 45° & 90° flexion) with three levels of elbow flexion angle (45°, 90° & 135°) were taken as levels of independent variables. There were 12 combinations available for each participant and the experiment was conducted on the basis of random order of experimental combinations for each participant. Discomfort score on 100 mm visual analogue scale (VAS) and Electromyography (EMG) activity of Extensor Carpi Radialis Brevis (ECRB) muscle were dependent variables for the analyses. The task for the experiment was of 150N ± 5N grip force at a frequency of 15 exertions/minute for five minutes duration. After performing the MANOVA on the recorded data, the results showed that the shoulder flexion/extension and elbow flexion both were highly significant (p < 0.001). Also it was found that −45° shoulder extension combined with 45° elbow flexion angle was the most discomfort posture. The practical relevance of the study is that, in industrial tasks such posture should be avoided to minimize risk of WMSDs.Relevance to industryThe findings in terms of relationship between discomfort/EMG vs. shoulder rotation combined with elbowflexion are important to design Industrial tasks with the reduced risk of WMSDs. Such as, sheet metal cutting, fabrication of sheet metal work, die casting, and drilling operations may require the shoulder movements in extenion/flexion combined with elbowflexion. |
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| Keywords: | Elbow flexion Shoulder flexion/extension Electromyography (EMG) Discomfort score |
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