The purpose of the present study was to assess the effect of commercial sports beverage intake after a thermal exposure on water-electrolytes balance.
Nine healthy male volunteers with a mean age of 26.4 years, not heat acclimated, participated in a control experiment where no fluid was given (C experiment) . Five of them were given 500ml isotonic sports beverage containing Na⁺, K⁺, Cl^-and glucose (S. B experiment) and/or 500 ml tap water (Wa experiment) immediately after sauna exposure. The nude subjects were exposed to a sauna with 65 to 70°C (r. h. 50 to 60%) for 30 min.
Serum protein, electrolytes (Na⁺, K⁺, Cl^-), creatinine, plasma aldosterone (Ald), and catecholamines concentrations and excretions of electrolytes and aldosterone into urine were measured before, and 3, 30, 60, and 120 min after the sauna. Serum and urinary osmolalities, blood pressure, rectal temperature (Tr), heart rate, oxygen consumption and weight loss were also measured.
Body weight loss ranged from 50 to 750g. Serum protein, electrolytes and Ald concentrations increased significantly after the sauna. The enhanced levels of these variables and the depression of urine volume, urinary Na⁺excretion were maintained throughout the 2h recovery period in C experiment. Hydration associated with a reduced concentration of serum protein and electrolytes was observed at 30 min in S. B, at 60 min in Wa, and a dehydration occured again at 120 min both in S. B and Wa. A peak of urine volume was observed at 60 min in S. B and at 120 min in Wa during recovery. Free water clearance (C_H2O) was -0.98 ml/min/100 ml GFR (Ccr) prior to the exposure. With no fluid administration after the sauna, an excess in negative water balance remained throughout the 2 h recovery. But C_H2Ochanged from negative to positive at 60 and 120 min after sports beverage and/or water loadings.
A significant elevation of % TRNa (0.33 to 1.14%) was maintained after the sauna in both C and Wa experiment. Plasma Aid concentration and excretion of Aid in urine after the exposure were higher in both C and Wa than in S. B experiment. The increased Tr did not return to the initial level throughout the recovery. No significant differences were observed among the three experiments in heart rate and blood pressure as well as Tr.
The data indicate that salt deficit due to the sauna exposure was attenuated, but not prevented, by sports beverage intake, although the Aid secretion was alleviated. It is suggested that an over loading of sports beverage or water (i. e. 500 ml VS 50 to 750 g weight loss) leads to a marked and prompt water-diuresis, and to another dehydration. The increase of Tr as well as a partly salt deficit can be related to the rises in Ald secretion still observed at 2 h recovery.

The present study was done to elucidate the medical problems and physical fitness of under-weight elementary schoolboys. Eighty nine volunteers, ranging in age from 9 to 12 yrs, were divided into five groups based on the grade of obesity, expressed as % of the standard, taking into account height, age and sex.
The mean grade of obesity for under-weight boys was -12 %, and this group was defined as the experimental group (group I; n=15) . The group III, which contained 23 boys of grade 0 %, and the group V made of 13 boys of grade +33.5 % was defined as the normal control and obese control, respectively.
The measurement of blood pressure, EKG recording, and blood sampling were done in the state of fasting before and after exercise. The exercise was a step test of 5 min duration with a temp of 1 step per 2 seconds, jumping over a bench 25 cm high for 9 years old boys, and 33 cm high for boys of 10 to 12 years. The step test score (PFI) and recovery rate of heart rate (RR (HR) ) were calculated from the EKG. The test battery of physical fitness performance was also done on another experimental day.
The serum levels of total cholesterol (TC), triglyceride (TG), total protein (TP) and hemoglobin (Hgb) were lower in experimental group (EG) than in control groups (CG) . The cholesterol-HDL/TC ratio was conversely higher in EG than in CG. There were no significant differences in the other biochemical measurements between the five groups.
Any abnormal EKG was not recorded before and after exercise throughout the subjects. The frequency of hypertension (above the 135/80 mmHg) was 10.2 % at pre-exercise time. But, none of the boys in EG was found to be hypertensive.
The PFI and physical fitness performance test score showed no differences between EG and group III, however, the score of group V was inferior to that of EG and/or group III. The RR (HR) in EG and over-weight group was lower compared to that for the average-weight boys.
Almost all components in blood measured were elevated after exercise in all the groups. The finding of the highest interest of the exercise-induced elevations of blood constituent levels was an increase in WBC measured as an indicator of stress. The magnitude of increase in WBC (ΔWBC) was higher in EG and the over-weight group than in the average-weight group. In normal subjects, ΔWBC was generally proportional to the work intensity, which, in the present exercise, depended upon the stature and body weight, because the height of bench, tempo and duration of exercise were same for all groups. The work intensity in EG was presumed milder, becasue the mean stature was slightly taller and bodyweight was less heavy compared to those in control groups. But, the greater increase of WBC in EG was observed in spite of a lighter work intensity. According to the Selye's literature, the particular WBC reaction to exercise in the under-weight boys was interpreted as a over-reaction to stress in the state of malnutrition.
From some biochemical parametors, the leaner subjects were assumed to be in a slight malnutrition. And also a later recovery of HR and over-reaction to exercise stress were shown in the under-weight boys group.
It is emphasized that the malnutrition resulting from excessive effort for preventing obesity was unfavourable for children in the growing stage for their healthy growth and development.