Exercise-induced decreases in sarcoplasmic reticulum Ca2+–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, V˙O2 peak = 3.39 ± 0.13 L min−1, mean ± SE), the resting Ca2+ ATPase activity (mol 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, Ca2+-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 Ca2+-ATPase were less pronounced (P < 0.05). These results indicate that muscle hypertrophy, although incapable of altering Ca2+-ATPase pump activity at rest, can attenuate the decrease observed in exercise by mechanism(s) as yet unknown.