Document Detail

Electromyographic manifestations of muscular fatigue.
MedLine Citation:
PMID:  7109886     Owner:  NLM     Status:  MEDLINE    
Analyses of surface electromyogram (EMG) power spectra and integrated EMG (IEMG) were performed during isometric fatigue contraction in eight male subjects. Fatigability was determined as the rate of rise in IEMG as a function of time (IEMG slope coefficient or eta). Results indicated that the IEMG slope coefficient for the biceps brachii at 40% of maximal voluntary contraction (MVC) was approximately nine times greater than that of the soleus. The exponential decay of maximal sustaining time (Ts) as a function of IEMG slope coefficient (Log Ts - = 0.895 x eta + 2.60, r = 0.92, P less than 0.001) during different fractions of MVC suggested a neurophysiological link between fatigability of the biceps and their motor unit (MU) activities which increased in an accelerated fashion. Analyses of mean power frequency (MPF) revealed that there was a significant decline in MPF (43.7 Hz, P less than 0.001) for the biceps brachii. Furthermore, the extent of this decline was correlated with MPF obtained during MVC (r = 0.96, P less than 0.000). This correlation indicated that MUs with higher MPF would fatigue to a greater extent than those with relatively lower MPF. Subsequent analyses of MPF during fatigue for the soleus revealed that there was a relatively small decline in MPF (7.3 Hz, P greater than 0.05). It was suggested that non-invasive analyses of power spectra and IEMG slope coefficient could provide a sensitive measure of MU fatigability that may reflect the activities of different types of muscle fibers.
T Moritani; A Nagata; M Muro
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Medicine and science in sports and exercise     Volume:  14     ISSN:  0195-9131     ISO Abbreviation:  Med Sci Sports Exerc     Publication Date:  1982  
Date Detail:
Created Date:  1982-10-21     Completed Date:  1982-10-21     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  8005433     Medline TA:  Med Sci Sports Exerc     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  198-202     Citation Subset:  IM; S    
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MeSH Terms
Isometric Contraction
Muscle Contraction
Muscles / physiology*

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

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