Time course of responses of human skeletal muscle to oxidative stress induced by nondamaging exercise

Previous studies in animals have demonstrated that a single period of aerob ic exercise induces a rise in the skeletal muscle activity of the antioxida nt enzymes superoxide dismutase and catalase and an increase in the muscle content of heat shock proteins (HSPs). The purpose of this study was to exa mine the time course of response of human skeletal muscle superoxide dismut ase and catalase activities and the content of HSP60 and HSP70 after a peri od of exhaustive, nondamaging aerobic exercise. Seven volunteers undertook one-legged cycle ergometry at 70% maximal oxygen uptake for 45 min. Biopsie s were obtained from the vastus lateralis muscle 7 days before and at 1, 2, 3, and 6 days after exercise. Muscle superoxide dismutase activity increas ed to a peak at 3 days postexercise, muscle catalase activities were unchan ged, and muscle content of HSP60 and the inducible HSP70 increased by varia ble amounts to reach means of 190% and 3,100% of preexercise values, respec tively, by 6 days postexercise. These data indicate that human skeletal mus cle responds to a single bout of nondamaging exercise by increasing superox ide dismutase activity and provide the first evidence of an increase in HSP content of human skeletal muscle after a submaximal exercise bout.