Document Detail

Neuromuscular response of young boys versus men during sustained maximal contraction.
MedLine Citation:
PMID:  12783054     Owner:  NLM     Status:  MEDLINE    
PURPOSE: This study was designed to compare neuromuscular response between boys and men during sustained maximal voluntary contraction (MVC). METHODS: Fifteen boys (YB, 10.5 +/- 0.9 yr) and 12 men (AM, 21.5 +/- 4.5 yr) participated in the experiment. Arm's cross sectional area (CSA) and maximal force (F(max)) of elbow flexor were measured before subjects performed a 30-s sustained MVC. Mean power frequency (MPF) and muscle fiber conduction velocity (MFCV) were calculated from myoelectric signals of the biceps brachii. F(max)/CSA, MPF, and MFCV changes were expressed by slopes of linear regressions. Maximal MPF (I-MPF) and MFCV (I-MFCV) were derived from the intercept of each regression. RESULTS: AM had significantly greater F(max)/CSA (P < 0.05), I-MPF (P < 0.05), and I-MFCV (P < 0.01) than YB. F(max)/CSA (P < 0.001), MPF (P < 0.001), and MFCV (P < 0.01) declined significantly more for AM than YB. MPF/MFCV ratio increased, i.e., MPF decreased more than MFCV, for both groups but this was significantly (P < 0.001) more pronounced for AM. CONCLUSION: Taken together, those results suggest that more fatigable Type II motor units are involved in men, resulting in greater lactic acid and ions accumulations during fatigue. This difference in muscle's metabolic and ionic state could be responsible for a greater reflex-induced decrease of motor units firing rates in men compared with boys. This firing rate decrease could be explained using the "muscular wisdom" hypothesis and would express a nervous command adaptation to sustain a maximal contraction.
Renaud Halin; Philippe Germain; Stephane Bercier; Bronislaw Kapitaniak; Olivier Buttelli
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Publication Detail:
Type:  Comparative Study; Journal Article    
Journal Detail:
Title:  Medicine and science in sports and exercise     Volume:  35     ISSN:  0195-9131     ISO Abbreviation:  Med Sci Sports Exerc     Publication Date:  2003 Jun 
Date Detail:
Created Date:  2003-06-03     Completed Date:  2003-09-04     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8005433     Medline TA:  Med Sci Sports Exerc     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1042-8     Citation Subset:  IM; S    
Laboratory of Motor Performance, Department of Ergonomic Conception and Motor Activity, U.F.R. S.T.A.P.S, University of Orléans, France.
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MeSH Terms
Age Factors
Elbow / physiology
Muscle Contraction / physiology*
Muscle Fatigue*
Muscle Fibers, Fast-Twitch / physiology*
Muscle, Skeletal / growth & development,  innervation*,  physiology*
Weight Lifting / physiology

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

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