Endurance training reduces the rate of diaphragm fatigue in vitro


VRABAS I. , DODD S., POWERS S., HUGHES M., COOMBES J., FLETCHER L., ...More

MEDICINE AND SCIENCE IN SPORTS AND EXERCISE, vol.31, no.11, pp.1605-1612, 1999 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 31 Issue: 11
  • Publication Date: 1999
  • Doi Number: 10.1097/00005768-199911000-00017
  • Title of Journal : MEDICINE AND SCIENCE IN SPORTS AND EXERCISE
  • Page Numbers: pp.1605-1612

Abstract

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 similar to 70% of (V) over dotO(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.