Study of the energy balance and the nutritional status of highly trained female swimmers

Abstract

Despite the high energy cost of their exercise training, female endurance athletes frequently report low to moderate energy intake, suggesting that they could be in a negative energy balance. This hypothesis was tested in the present study by studying six elite female swimmers performing about 15 hrs of training/week. Their daily energy needs were assessed during a 30 day cycle of training being representative of their annual training schedule. Three-day dietary and activity records as well as body composition measurements were performed at the beginning and at the end of the study. A mean daily energy intake of 2472±717 kcal (±SD) was observed during the testing period. This intake corresponded to 108% of the recommended dietary allowance (RDA) for sedentary female subjects of the same weight. The mean energy expenditure (2676±500 kcal/day) did not differ significantly from the mean energy intake (p>0.05). The body composition measurements showed a slight increase in fat-free mass during the study, while body weight and fat mass remained unchanged. Low plasma ferritin levels were observed in some subjects and this was associated with low iron intake. Resting metabolic rate did not change during the course of the training cycle. Results of this study show that energy intake was adequate to satisfy the increase in energy expenditure associated with training. This suggests that their energy needs were substantially lower than those which would have been predicted on the basis of the extra caloric cost of exercise and the usual energy expenditure of sedentary individuals.