Document Detail

Inactivity, age, and exercise: single-muscle fiber power generation.
MedLine Citation:
PMID:  23104693     Owner:  NLM     Status:  MEDLINE    
We examined the effects of mild therapeutic exercise during a period of inactivity on size and contractile functions of myosin heavy chain (MHC) type I (n = 204) and type II (n = 419) single fibers from the medial gastrocnemius in three age groups. Young adult (5-12 mo), middle-aged (24-31 mo), and old (32-37 mo) F344BNF1 rats were assigned to one of three groups: weight-bearing control, non-weight bearing (NWB), and NWB plus exercise (NWBX). Fourteen days of hindlimb suspension were applied in NWB rats. The NWBX rats exercised on the treadmill for 15 min, four times a day, during the period of NWB. The NWBX did not improve peak power, but increased normalized power of MHC type I fibers in young adult rats. In MHC type II fibers, NWBX did not change peak power, isometric maximal force, V(max), and fiber size from young adult and middle-aged rats. NWBX did not improve peak power and isometric maximal force and showed a dramatic decline in V(max) and normalized power in the old rats. Collectively, mild treadmill exercise during a period of inactivity does not improve peak power of MHC type I or type II fiber from the gastrocnemius in young, middle-aged, and old rats. However, NWBX is beneficial in enhancing normalized power of MHC type I fibers in young adult rats, most likely due to the stimulus intensity and the ability of the individual fibers to adapt to the stimulus. In contrast, several factors, such as impaired adaptation potential, inappropriate exercise intensity, or increased susceptibility to muscle damage, may contribute to the lack of improvement in the older rats.
Jong-Hee Kim; Ladora V Thompson
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2012-10-25
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  114     ISSN:  1522-1601     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-01-02     Completed Date:  2013-07-08     Revised Date:  2014-01-09    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  90-8     Citation Subset:  IM    
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MeSH Terms
Adaptation, Physiological / physiology
Aging / physiology*
Atrophy / physiopathology
Hindlimb / physiology
Hindlimb Suspension / physiology
Muscle Contraction / physiology*
Muscle Fibers, Skeletal / physiology*
Myosin Heavy Chains / metabolism
Physical Conditioning, Animal / physiology*
Rats, Inbred F344 / physiology
Weight-Bearing / physiology
Grant Support
Reg. No./Substance:
EC Heavy Chains

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

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