Duration of differential activations is functionally related to fatigue prevention during low-level contractions |
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| Authors: | A Holtermann C Grönlund J Ingebrigtsen JS Karlsson K Roeleveld |
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| Institution: | 1. Human Movement Sciences Programme, Norwegian University of Science and Technology, Trondheim, Norway;2. National Research Centre for the Working Environment, Lersø Parkallé 105, 2100 Copenhagen Ø, Denmark;3. Department of Biomedical Engineering and Informatics, University Hospital, Umeå, Sweden and Centre for Biomedical Engineering and Physics, Umeå University, Umeå, Sweden;1. School of Electronic, Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China;2. Human Spaceflight System Engineering Division, Institute of Manned Space System Engineering, CAST, Beijing, PR China;3. School of Hotel and Tourism Management, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong;1. Chair of Analytical Chemistry, Department of Chemistry, Tallinn University of Technology, 19086 Tallinn, Estonia;2. Laboratory of Industrial Chemistry and Reaction Engineering, Johan Gadolin Process Chemistry Centre, Åbo Akademi University, FI-20500 Åbo-Turku, Finland;3. Technical Chemistry, Department of Chemistry, Chemical-Biological Centre, Umeå University, SE-901 87, Umeå, Sweden;1. School of Water Conservancy & Environment, Zhengzhou University, Zhengzhou 450001, China;2. State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China;1. Department of Applied Educational Science, Umeå University, Sweden;2. Department of Psychology, Umeå University, SE-901 87 Umeå, Sweden |
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| Abstract: | The aim of this study was to investigate the importance of duration of differential activations between the heads of the biceps brachii on local fatigue during prolonged low-level contractions. Fifteen subjects carried out isometric elbow flexion at 5% of maximal voluntary contraction (MVC) for 30 min. MVCs were performed before and at the end of the prolonged contraction. Surface electromyographic (EMG) signals were recorded from both heads of the biceps brachii. Differential activation was analysed based on the difference in EMG amplitude (activation) between electrodes situated at the two heads. Differential activations were quantified by the power spectral median frequency of the difference in activation between the heads throughout the contraction. The inverse of the median frequency was used to describe the average duration of the differential activations. The relation between average duration of the differential activations and the fatigue-induced reduction in maximal force was explored by linear regression analysis. The main finding was that the average duration of differential activation was positively associated to relative maximal force at the end of the 30 min contraction (R2 = 0.5, P < 0.01). The findings of this study highlight the importance of duration of differential activations for local fatigue, and support the hypothesis that long term differential activations prevent fatigue during prolonged low-level contractions. |
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