MUSCLE HYPERTROPHY INDUCED BY HEAT-STRESS WITH LOW-INTENSITY EXERCISE IN HEALTHY HUMANS

摘要

Effects of low-intensity exercise (LIE) with heat-stress on muscle hypertrophy were investigated. Five healthy men were subjected to 10 weeks of LIE for elbow flexor muscles {4 days/wk at less than 30 repetition maximum (RM), 3 sets (20 repetitions) of flexion-extension exercise of elbow joint in the left non-dominant hand}. Application of heat-stress was performed at the same time as elbow exercise on upper left arm by using a heating pad with 2 sets of 30-min heating with 5-min interval. Maximum isometric force in flexion significantly increased in trained (14%) and untrained arm (10%) after LIE (p<0.05). Significant increment (12%) in the mean cross-sectional area of biceps brachii muscles in the left arm was observed (p<0.05). Evidences strongly indicated that exercise training at an intensity even lower than 50% 1 RM could be effective in increasing of muscle strength with muscle hypertrophy, when the training was combined with heating. These results suggest that heat-stress might be a useful countermeasure for muscular atrophy during space flight as well as rehabilitation.