Document Detail

Muscle fiber involvement during training of different intensities and durations.
MedLine Citation:
PMID:  178189     Owner:  NLM     Status:  MEDLINE    
The extent of skeletal muscle fiber type involvement during exercise training was evaluated by assessing the increase in oxidative markers in the muscles of rats trained by various exercise programs. Rats were trained by running 6 days/wk at 1 mph for 12 wk by one of four protocols: group I-10% grade, 2 h/day; group II-10% grade, 4 h/day; group III-30% grade, 40 min/day; and group IV-30% grade, 2 h/day. No distinction was found between the different programs for the increase in cytochrome c content or citrate synthase (CS) activity of mixed muscle. The more intense programs utilizing a 30% grade induced an increase in CS activity in the fast-twitch white (FTW) fiber that was twice that found in the 10% grade groups. The fast-twitch red (FTR) fibers of the 2 h/day or more groups showed a similar increase (90-95%) in CS activity except for the group that ran for only 40 min/day. These data suggest that: 1) running durations of moderately intense exercise longer than 2 h/day do not further increase the oxidative capacity of the working muscles; and 2) more intense exercise builds on the performance of previously used FTR fibers and additionally involves the low oxidative FTW fibers.
R L Terjung
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American journal of physiology     Volume:  230     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1976 Apr 
Date Detail:
Created Date:  1976-07-06     Completed Date:  1976-07-06     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  946-50     Citation Subset:  IM; S    
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MeSH Terms
Body Weight
Citrate (si)-Synthase / metabolism*
Cytochrome c Group / metabolism*
Muscles / enzymology,  physiology*
Organ Size
Oxo-Acid-Lyases / metabolism*
Physical Conditioning, Animal
Physical Exertion*
Time Factors
Reg. No./Substance:
0/Cytochrome c Group; EC (si)-Synthase; EC 4.1.3.-/Oxo-Acid-Lyases

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

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