Serial effects of high-resistance and prolonged endurance training on Na+–K+ pump concentration and enzymatic activities in human vastus lateralis

The purpose of this study was to compare two contrasting training models, namely high-resistance training and prolonged submaximal training on the expression of Na⁺–K+ ATPase and changes in the potential of pathways involved in energy production in human vastus lateralis. The high-resistance training group (VO _2peak = 45.3 ± 1.9 mL kg^?1 min^?1, mean ± SE, n = 9) performed three sets of six to eight repetitions maximal, each of squats, leg presses and leg extensions, three times per week for 12 weeks, while the prolonged submaximal training group (VO _2peak = 44.4 ± 6.6 mL kg^?1 min^?1, n = 7) cycled 5–6 times per week for 2 h day^?1 at 68% VO _2peak for 11 weeks. In the HRT group, Na⁺–K⁺ ATPase (pmol g^?1 wet wt), measured with the ³H-ouabain binding technique, showed no change from 0 (289 ± 22) to 4 weeks (283 ± 15), increased (P < 0.05) by 16% at 7 weeks and remained stable until 12 weeks (319 ± 19). For prolonged submaximal training, a 22% increase (P < 0.05) was observed from 0 (278 ± 31) until 3 weeks (339 ± 29) with no further changes observed at either 9 weeks (345 ± 25) or 11 weeks (359 ± 34). In contrast to high-resistance training, where a 15% increase (P < 0.05) was observed, only in the maximal activity of phosphorylase, prolonged submaximal training resulted in increases in malate dehydrogenase, β-hydroxyl-CoA dehydrogenase, hexokinase and phosphofructokinase. In contrast to high-resistance training which failed to result in an increase in VO _2peak, prolonged submaximal training increased VO _2peak by ≈15%. Only for prolonged exercise training was a relationship observed for VO _2peak and Na⁺–K⁺-ATPase (r = 0.59; P < 0.05). Correlations between VO _2peak and mitochondrial enzyme activities were not significant (P > 0.05) for either training programme. It is concluded that although both training programmes stimulate an up-regulation in Na⁺–K⁺ ATPase concentration, only the prolonged submaximal training programme enhances the potential for β-oxidation, oxidative phosphorylation and glucose phosphorylation.     

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˙O ₂ peak = 3.39 ± 0.13 L min^?1, mean ± SE), the resting Ca²⁺ ATPase activity (μmol 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% VO ₂ peak and (P < 0.05) a further 19% during 30 min at 72% VO ₂ 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.