EFFECT OF THE WELL-REGULATED DIET ON BODY COMPOSITION AND PHYSICAL WORKING CAPACITY OF FEMALE COLLEGE GYMNASTS / 体力科学

ABSTRACT

Competitive gymnasts are confronted with the problem of weight loss before a competition. They intend to decrease body fat, but not muscle. One of the most reasonable method for the purpose is a dieting. Neverthless, a dieting often leads to decrease not only body fat but also lean body weight (LBW) of which 47% is composed of muscle. That is, a dieting has the possibility of decreasing the competitive performance. The well-regulated diet is, therefore, required very much for weight loss of the gymnasts. The body composition (under-water weighing), physical working capacity (submaximal endurance capacity, muscle strength and vertical jump) and blood constituents of seven female gymnasts were measured before and after the 33 day-diet. They, ranging from 18 to 22 years of age, were high ranked athletes in Japan. The diet program was arranged by the dietitian taking gymnasts' favours into consideration. The averaged daily diet evaluated by means of a dietary recall had 1194 kcal with 54.7g of protein, 28.5g of fat and 179.9g of carbohydrate. On the other hand, the usual intakes just before the dieting were 1722 kcal in energy, 43.0g in protein, 57.1g in fat and 269.2g in carbohydrate. All the intakes of vitamins and minerals of the diet were higher than the Japanese recommended dietary allowance (RDA) . They practiced about four hours a day, six days a week, during the diet period. The daily energy expenditures before and at the last stage of the dieting were 2332 kcal and 2551 kcal on the average respectively, which were estimated through motion and time study. After the dieting body weight decreased significantly from 52.11kg to 48.35kg, of which difference was composed of 2.99kg of body fat and 0.77kg of LBW. The decrease of body fat was statistically significant, but LBW was not so. Concerning all the physical working capacities in oxygen uptake and heart rate, muscle strength except trunk extension strength, and vertical jump, there were no significant changes after the dieting. But respiratory exchange ratio (R) decreased significantly at the same work loads. This decrease suggested increased usage of stored body fat as energy during daily practice, and might support the significant decrease of body fat. Most of blood constituents were still in normal ranges in spite of significant changes. Marked change was found in serum FFA which increased three times after the dieting. This change also meant the increased usage of body fat after the dieting. These data indicated that the diet program arranged in this study proved successful and the wellregulated diet was very effective in conditioning the body composition and the physical working capacity of female gymnasts.