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Motor unit synchronization during fatigue: described with a novel sEMG method based on large motor unit samples.
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
2009 (English)In: Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology, ISSN 1873-5711, Vol. 19, no 2, 232-241 p.Article in journal (Refereed) Published
Abstract [en]

The amount of documented increase in motor unit (MU) synchronization with fatigue and its possible relation with force tremor varies largely, possibly due to inhomogeneous muscle activation and methodological discrepancies and limitations. The aim of this study was to apply a novel surface electromyographical (EMG) descriptor for MU synchronization based on large MU populations to examine changes in MU synchronization with fatigue at different sites of a muscle and its relation to tremor. Twenty-four subjects performed an isometric elbow flexion at 25% of maximal voluntary contraction until exhaustion. Monopolar EMG signals were recorded using a grid of 130 electrodes above the biceps brachii. Changes in MU synchronization were estimated based on the sub-band skewness of EMG signals and tremor by the coefficient of variation in force. The synchronization descriptor was dependent on recording site and increased with fatigue together with tremor. There was a general association between these two parameters, but not between their fluctuations. These results are in agreement with other surface EMG studies and indicate that the novel descriptor can be used to attain information of synchronization between large MU populations during fatigue that cannot be retrieved with intra-muscular EMG.

Place, publisher, year, edition, pages
2009. Vol. 19, no 2, 232-241 p.
Keyword [en]
Force tremor, electrode location, multi-channel surface EMG, motor unit synchronization, fatigue
URN: urn:nbn:se:umu:diva-25809DOI: 10.1016/j.jelekin.2007.08.008PubMedID: 18207421OAI: diva2:233937
Available from: 2009-09-03 Created: 2009-09-03 Last updated: 2011-08-24

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Grönlund, ChristerKarlsson, J Stefan
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Radiation Physics

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