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 (Peer-Reviewed Journal) identifier identifier

  • Publication Type: Article / Article
  • Volume: 31 Issue: 11
  • Publication Date: 1999
  • Doi Number: 10.1097/00005768-199911000-00017
  • Journal Name: MEDICINE AND SCIENCE IN SPORTS AND EXERCISE
  • Journal Indexes: Science Citation Index Expanded, Scopus
  • 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.