Muscle Endurance Performance Enhancement without Increase in Maximal Muscle Oxygen Consumption

Abstract

The purpose of this study was to investigate how 6 weeks of handgrip endurance exercise training affects maximal muscle O₂ consumption (muscle V·O₂) during incremental handgrip exercise and muscle energetics during high intensity exercise. Eight healthy female subjects performed dynamic handgrip exercise training until exhaustion at 30% of maximum voluntary contraction at 1 set per day for 6 weeks. The measurement site was the right finger flexor muscles. Muscle V·O₂ was evaluated using near-infrared continuous wave spectroscopy during incremental handgrip exercise pre- and post-training. Both phosphocreatine (PCr) and muscle pH during exercise were evaluated using 31-phosphorus magnetic resonance spectroscopy. After the training, performance time was significantly longer than pre-training (52.9±3.5 and 84.5±5.8 s, pre- and post-training respectively) (p<0.05). No significant difference of maximal muscle V·O₂ was found between pre- and post-training (18.3±1.9 and 18.1±1.2 fold of resting). Maximal exercise workload was significantly greater post-training than pre-training. PCr and muscle pH levels at exhaustion were unchanged between pre- and post-training. These findings have significant implications for the development of exercise tolerance under severe metabolic acidosis.