Document Detail

Periodic increases in force during sustained contraction reduce fatigue and facilitate spatial redistribution of trapezius muscle activity.
MedLine Citation:
PMID:  17520244     Owner:  NLM     Status:  MEDLINE    
This study compared fatigue and the spatial distribution of upper trapezius electromyographic (EMG) amplitude during a 6-min constant force shoulder elevation task at 20% of the maximal voluntary contraction force (MVC) (constant force) and during the same task interrupted by brief (2 s) periodic increases in force to 25% MVC every 30 s (variable force). Surface EMG signals were recorded with a 13 x 5 grid of electrodes from the upper trapezius muscle of nine healthy subjects. The centroid (center of activity) of the EMG root mean square map was computed to assess changes over time in the spatial distribution of EMG amplitude. MVC force decreased by (mean +/- SD) 9.0 +/- 3.9% after the constant force task (P < 0.05) but was unchanged following the variable force contraction. The centroid of EMG amplitude shifted in the cranial direction across the duration of the variable force contraction (P < 0.05) but not during the constant force contraction (shift of 2.9 +/- 2.3 mm and 1.4 +/- 1.1 mm, respectively). The results demonstrate that periodic increases in force during a sustained contraction enhance the modifications in spatial distribution of upper trapezius EMG amplitude and reduce fatigue compared to a constant force contraction performed at a lower average load. The change in spatial distribution of EMG amplitude over time during a sustained contraction may reflect a mechanism to counteract fatigue during prolonged muscle activity.
Deborah Falla; Dario Farina
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2007-05-23
Journal Detail:
Title:  Experimental brain research     Volume:  182     ISSN:  0014-4819     ISO Abbreviation:  Exp Brain Res     Publication Date:  2007 Sep 
Date Detail:
Created Date:  2007-08-27     Completed Date:  2008-02-07     Revised Date:  2013-12-13    
Medline Journal Info:
Nlm Unique ID:  0043312     Medline TA:  Exp Brain Res     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  99-107     Citation Subset:  IM    
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MeSH Terms
Analysis of Variance
Data Interpretation, Statistical
Isometric Contraction / physiology
Muscle Contraction / physiology
Muscle Fatigue / physiology*
Muscle, Skeletal / physiology*
Shoulder / physiology

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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