Exercise-induced decreases in sarcoplasmic reticulum Ca(2+)-ATPase activity attenuated by high-resistance training

Muscle biopsies were performed on the vastus lateralis muscle prior to and during a high-resistance training (HRT) programme in order to examine the effects of hypertrophy on sarcoplasmic reticulum Ca2+ ATPase activity at rest and during exercise. In six male untrained volunteers (peak aerobic power, Vo2 peak = 3.39 +/- 0.13 L min-1, mean +/- SE), the resting Ca2+ ATPase activity (mumol-min-1 g wet wt-1) at 0 (4.89 +/- 0.20), 4 (5.62 +/- 0.56), 7 (5.15 +/- 0.41) and 12 (4.82 +/- 0.11) weeks was unchanged by HRT. During cycle ergometer exercise, prior to training, Ca(2+)-ATPase was reduced (P < 0.05) by 14% during the initial 30 min at 58% Vo2 peak and (P < 0.05) a further 19% during 30 min at 72% Vo2 peak. Following 7 and 12 weeks of training, the decreases in SR Ca(2+)-ATPase were less pronounced (P < 0.05). These results indicate that muscle hypertrophy, although incapable of altering Ca(2+)-ATPase pump activity at rest, can attenuate the decrease observed in exercise by mechanism(s) as yet unknown.