Effects of drinking on sweating and body cooling during exercise / 体力科学

To examine the effects of water replacement on sweating and body cooling during exercise, We studied the sweat rate, changes in body weight and body temperature during exercise with or with-out drinking various amounts of water. The subjects had been dehydrated or normally hydrated prior to exercise.<BR>1. Rectal temperature increased significantly with body weight loss.<BR>2. Sweat rate during exercise was constant (968-996 g/h) regardless of whether the subjects were dehydrated or hydrated.<BR>3. Body weight loss was negatively correlated with the amount of water intake, but was not correlated with the total amount of sweating.<BR>4. Total heat loss increased with increased water intake, and corresponded to 1345% of heat storage during exercise without drinking.<BR>These results suggest that although water replacement during exercise dose not affect the sweat rate, it has physiological significance in the maintenance of body fluid, and a physical effect in terms of body cooling.

Cardiovascular function during kendo exercise in a hot environment. Effects of water replacement / 体力科学

A study was carried out to examine the effects of water replacement on cardiovascular function during kendo practice in a hot environment. Five male college kendoists performed moderately severe 30-min kendo practice at a WBGT index of about 27°C with and without water intake. For water replacement, the subjects ingested 700 ml water (500 ml before exercise and 200 ml at 15 min after the start of exercise) . Under both conditions, body weight was decreased significantly, and hematocrit and serum total protein concentration were increased significantly after the exercise. With water replacement, the body weight loss induced by the exercise was similar to that under water deprivation. However, the decrease in body weight from the basal body weight, i. e. body weight measured before water intake, was significantly less with water replacement than under water deprivation. There were no significant differences in the percentage increases of hematocrit and serum total protein concentration between the two conditions, although the percentage change in plasma vasopressin concentration was significantly lower with water replacement than without. In the subjects deprived of water, the left ventricular end-diastolic dimension and left atrial dimension were significantly reduced after the exercise, and stroke volume, ejection fraction, and fractional shortening were also decreased significantly. The ratio of left ventricular end-systolic wall stress to left ventricular end-systolic volume index was increased significantly after the exercise without water intake. With water replacement, however, the percentage decreases in cardiac dimensions, stroke volume, ejection fraction, and fractional shortening were significantly lower than those under water deprivation. There was no significant change in the ratio of left ventricular end-systolic wall stress to left ventricular end-systolic volume index before and after the exercise with water intake. It is suggested that 700 ml water replacement before and during kendo exercise in a hot environment prevents depletion of stroke volume and deterioration of cardiovascular function, although it might not improve significantly the plasma volume loss after exercise.