Document Detail

Fatigue effects on motor unit activity during submaximal contractions.
MedLine Citation:
PMID:  10987164     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: To examine motor unit changes during the development of fatigue in healthy subjects. DESIGN: Automated decomposition-enhanced spike-triggered averaging was used to characterize motor unit size and firing rate in the dominant vastus medialis during maintained contractions at 10% and 30% of maxima voluntary contraction (MVC). SETTING: Academic outpatient neuromuscular clinic. PARTICIPANTS: Healthy laboratory personnel. MAIN OUTCOME MEASURES: Surface electromyogram, surface-detected motor unit action potential amplitude (S-MUAP), mean firing rate, force (MVC), motor unit index. RESULTS: Surface electromyogram values and S-MUAP amplitudes increased during both 10% and 30% MVC fatiguing contractions, while mean firing rates decreased. A motor unit index, indicating the degree of motor unit pool activation, increased similarly to S-MUAP size, implying that new and larger units were recruited to maintain the contraction. Repeated contractions led to earlier motor unit changes and fatigue. CONCLUSION: During submaximal fatiguing contractions, additional motor units are activated to maintain strength. These changes begin early, within the first minute, particularly after a previous fatiguing effort.
R A Conwit; D Stashuk; H Suzuki; N Lynch; M Schrager; E J Metter
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Publication Detail:
Type:  Clinical Trial; Journal Article    
Journal Detail:
Title:  Archives of physical medicine and rehabilitation     Volume:  81     ISSN:  0003-9993     ISO Abbreviation:  Arch Phys Med Rehabil     Publication Date:  2000 Sep 
Date Detail:
Created Date:  2000-09-26     Completed Date:  2000-09-26     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  2985158R     Medline TA:  Arch Phys Med Rehabil     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1211-6     Citation Subset:  AIM; IM    
Department of Neurology, Johns Hopkins Bayview Medical Center, Baltimore, MD 21224, USA.
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MeSH Terms
Action Potentials
Electric Stimulation
Fatigue / physiopathology*
Middle Aged
Muscle Contraction / physiology*
Muscle, Skeletal / physiology*

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