Purpose: The present study examined the effects of endurance training on the contractile and biochemical properties of the rat costal diaphragm in vitro. Methods: Sixty-four rats were divided into two groups: exercise trained (T) and control (C). Training consisted of treadmill running 5 d·wk -1 , 60 min·d -1 at ~70% of V̇O(2max), over a 10-wk period. Results: Control diaphragm strips produced an average of 12% less force from minute 15 to 50 of a 60-min in vitro fatigue protocol, compared with the T diaphragm strips (P < 0.01). T diaphragms had 10.1% higher citrate synthase (CS) and 12.1% higher superoxide dismutase (SOD) activities compared with the C (P < 0.05). Despite a significant decrease (P < 0.05) in Type IIb myosin heavy chains (MHC) and an increase (P < 0.05) in Type I MHC in T diaphragms, maximal shortening velocity (V(max)) in the diaphragm was not different between T and C animals. No differences were observed in specific force or the relative proportions of myosin light chains between groups. Conclusions: These findings suggest that endurance training reduces the rate of diaphragm fatigue in vitro but has no effect on V(max) or specific force.

Item Type:	Refereed Article
Research Division:	Medical and Health Sciences
Research Group:	Human Movement and Sports Science
Research Field:	Exercise Physiology
Objective Division:	Health
Objective Group:	Clinical Health (Organs, Diseases and Abnormal Conditions)
Objective Field:	Skeletal System and Disorders (incl. Arthritis)
Author:	Coombes, JS (Dr Jeff Coombes)
ID Code:	17378
Year Published:	1999
Web of Science® Times Cited:	22
Deposited By:	Secondary and Post-Compulsory Education
Deposited On:	1999-08-01
Last Modified:	2000-05-05
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