There is no doubt that sweating, changes in body temperature and changes in circulatory function are main physiological changes induced by heat exposure and that these physiological changes may be used to assess a so called “heat tolerance” of each person. It will be natural to inquire what combination of these physiological changes is the best index for the evaluation of “heat tolerance”. It may be presumed that there is an underlying factor which is called as “heat tolerance” and that this factor controls various physiological changes induced by heat exposure simultaneously. If this hypothesis is true, the factor which may be expressed as a transformed variate of various physiological changes must be the best index for the evaluation of “heat tolerance”. The above hypothesis has been tested by applying a statistical method called “principal components analysis” to the data on several physiological changes when young healthy male subjects were compelled to exercise in a warm bath.
The purpose of this study was to determine maximum oxygen intake and its relation to body weight of Japanese ordinary adolescents who consisted of 266 boys and 280 girls (12-18 years of age) living in Nagoya City. The progressive treadmill exercise test was chosen as a work stimulus. Treadmill test was made with a constant slope of 8.6%. During the first 2 minutes, the treadmill was set in motion at a certain speed (160m/min for boys and 140m/min for girls), and then the speed was increased by lOm/min every succeeding minute until exhaustion. Expired air during running was collected in Douglas bag every 1 minute upto exhaustion. Then sampling gas was analyzed by means of a Beckman oxygen and carbon dioxide analyzer. The heart rate was calculated from ECG during running and the respiratory rate was determined with the aid of thermister attached to the inside of the mask. All experiments were performed in the afternoon (PM 3 : 00-5: 00) during the winter seasons from 1968 to 1970. The results obtained in this study were as follows; 1) The mean value of maximum oxygen intake of the boys remarkably increased with age until 18 years of age. The maximum value was 2.81 l/mmn at 18 years of age. On the other hand, the mean value of the girls was almost constant over a wide range of ages from 12 to 18 except between 16 and 17. The maximum value was 1.941/min at 17 years of age. 2) The correlation coefficients and the regression equations were calculated between maximum oxygen intake and body weight. Boys r=0.883 Y= 0.0457X+ 0.0902 ± 0.3094 (n; 260) Girls r=0.595 Y=0.0149X+1.0648±0.2565 (n; 288) Where Y is maximum oxygen intake in l/min and X is body weight in kg. The same correlation coefficients and regression equations were calculated relating to sex and age. As for boys, the coefficients of “X” in the regression equations increase with age from 0.0227 at 12 years of age to 0.0468 at 18 years of age. On the other hand, there was no distinct inclination in the regression equations of the girls.
The present study was intended to determine max. Vo2 and its relation to body weight of Japanese athletes. The subjects in this study were 151 male and female athletes who were Japanese excellent or good runners and swimmers. Max. Vo22 was determined during the maximum running on the treadmill. Treadmill test was made with a constant slope of 8.6%. During the first 2 minutes, the treadmill was set in motion at a certain speed (180 or 200 m/min for male and 160 m/ min for female), and then the speed was increased by 10 m/min every succeeding minute until exhaustion. Expired air during running was collected in Douglas bag every 1 minute upto exhaustion. The sampling gas was analyzed by means of a Beckman oxygen and carbon dioxide analyzer. The results obtained in this study were as follows ; 1) The regression equations were calculated between max. Vo2 and body weight in relation to sex and sports (Table 1) . 2) Max. Vo2 per body weight of the male swimmers ranges from 50 to 70 and that of the male runners is 70 ml/kg/min. For the female swimmers max. Vo2 is between 40 and 60 and the female runners approximately 60 ml/kg/min. 3) The regression equation was calculated between the mean speed of 5000 m running as performance (Y) and max. Vo2 per body weight as physical resources (X) for the runners. Y=0. 0431X+2.50±0.232