Adaptations to endurance training at three intensities of exercise

Abstract

This study was undertaken to investigate the influence of exercise intensity (running speed) on a number of alterations that are known to occur with exercise training. Rats were trained on 3 treadmill running schedules: 20 m/min, 27 m/min and 35 m/min for 1 h/day. After 6 wk, lean body mass and body fat content were decreased to the same extent in all 3 trained groups. Thus, exercise appears to lower body fat by some mechanism that is not related to the amount of energy expended during exercise. Heart and adrenal gland weight-to-lean body mass ratio increased with increasing intensity of exercise but the adrenal weight-to-lean body mass ratios was independent of exercise intensity. Training increased muscle succinate dehydrogenase activity to the same extent in all 3 trained groups which suggests that the adaptation in respiratory capacity is not altered greatly by the intensity of training.