Regional training-induced alterations in diaphragmatic oxidative and antioxidant enzymes.

We examined the relationship between the intensity and duration of exercise training and the up-regulation of diaphragmatic oxidative and antioxidant enzyme activities. Nine groups of rats exercised for 10 weeks (4 days/week). Groups of animals exercised at three intensities (low, moderate, and high); at each exercise intensity, a group of animals ran at one of three exercise durations (30, 60, and 90 min/day). Sedentary animals served as controls. Muscle oxidative capacity was assessed by citrate synthase (CS) activity while antioxidant capacity was evaluated by total superoxide dismutase (SOD) and total glutathione peroxidase (GPX) activities. All intensities and durations of exercise training promoted significant (P < 0.05) increases in costal diaphragmatic CS, SOD, and GPX activities. Increases in costal CS, SOD, and GPX activity were independent of the exercise intensity and duration. High and moderate intensity exercise of 90 min duration significantly elevated (P < 0.05) crural diaphragm CS activity. Further, high and moderate intensity exercise of durations > or = 60 min promoted significant (P < 0.05) increases in crural diaphragm SOD activities. Exercise did not influence (P > 0.05) crural diaphragm GPX activity. We conclude that the training threshold for up-regulation of oxidative and antioxidant enzyme activities differs between the costal and crural diaphragm.