抄録
Effects of 8-weeks low-intensity aerobic training on the body composition and basal metaboli sm were evaluated in untrained young females. Twelve subjects randomly divided into two groups. One group was sedentary control. The other half exercised at an intensity of 50% of the maximal aerobic capacity for 30 minutes per day, 4days a week for 8 weeks. Altough maximal aerobic capacity was improved by training the body weight, percent of fat, and lean body mass were not different between before and after training. The basal metabolic rates (BMR), expressed by per day, per body weight, and per lean body mass, decreased significantly (p<0.05) after training, -9%, -8%, -8%, respectively. The blood thyroid hormone, T3, concentration was significantly reduced after training (p<0.001), and T4 and free T4 concentrations also decreased significantly (p<0.05). However, no significant correlation was observed between the decrease of the thyroid hormone level and that of BMR. There were no differense in the daily energy intake of the subjects between before and after training. Interestingly, the estimated daily energy expenditure was reduced after training. This might be related to an increase of sleep-time, and decrease of daily activity level. These results suggest that 8-weeks low-intensity aerobic training did not change body composition in untrained young females, because training resulted reducing the daily activity level, and consequently decreased of BMR and blood thyroid hormone concentrations.
