Effect of strenuous strength training on the Na-K pump concentration in skeletal muscle of well-trained men

This study examined how strenuous strength training affected the Na-K pump concentration In the knee extensor muscle of well-trained men and whether l eg muscle strength and endurance was related to the pump concentration. Fir st, the pump concentration, taken as H-3-ouabain binding, was measured in t op alpine skiers since strength training is important to them. Second, well -trained subjects carried out strenuous eccentric resistance training eithe r 1, 2, or 3 times . week(-1) for 3 months. The Na-K pump concentration, th e maximal muscle strength in a full squat lift tone repetition maximum, I R M), and the muscle endurance, taken as the number of full squat lifts of a mass of 70% of the 1 RM load, were measured before and after the training p eriod. The mean pump concentration of the alpine skiers was 425 (SEM 11) nm ol . kg(-1) wet muscle mass. The subjects in part two increased their maxim al strength in a dose-dependent manner. The muscle endurance increased for all subjects but independently of the training programme. From a mean start ing value of 356 (SEM 6) nmol . kg(-1) the mean Na-K pump concentration inc reased by 54 (SEM 15) nmol . kg(-1) (+15%, P < 0.001) when the results for all subjects were pooled. The effect was larger for those who had trained t wice a week than for those who had trained only once a week (P = 0.025), su ggesting that the effect of strength training depended on the amount of tra ining carried out. The muscle strength and endurance were not related to th e pump concentration, suggesting that the pumping power of this enzyme did not limit the performance during heavy lifting. However, the individual imp rovements in the endurance test during the training period correlated with the individual changes in the pump concentration (r(Spearman) = 0.5; P = 0. 01) which could mean that a common factor both increases the pump concentra tion and makes the muscles more adapted to repeated heavy lifting.