Four subjects each of the young and middle-aged, males and females were exposed to 16, 18, 20, or 22°C on the separate days. Relative humidity was 50% and air velocity was 18 cm/s. They kept rest on chairs for 60 minutes and then performed a sedentary work and a muscular mork ; stepping up and down for 15cm high platform 12 tims/min for 45 minutes each. Metabolic rate of the sedentary work was 45-60 kcal/m²h and that of the muscular work was 110-120 kcal/m²h. Clothes were prepared previously for each subject as they could choose and change the clothes according to their thenTlal sensations. The clothing conditions at rest under each thermal condition were almost the same as those during the sedentary and muscular work. Aithough there was a close relationship between room temperature exposed and clo-value of the clothes assembly chosen by the subjects, a warm sensation still arose by the increase of the the room temperature. From the relationships among the room temperature, clothing condition and therrnal sensation, clothing assembly of 1.0 (young males) to l.5 (middle-aged females) clo was necessary in 18°C and 0.8 to 1.3 clo in 20°C at rest. During muscular work, the necessary clothing assembly was decreased by about 0.1 clo in comparison with at rest.

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Nineteen adult females performed an exhausting series of treadmill walks for determinations of maximal oxygen intake under three air temperature conditions of 20°C, 30°C, and 40°C. The relative humidity was kept at 50% throughout. The value of maximal oxygen intake at 30°C was the largest among those tested here and the effect of quadratic component of air temperature factor on maximal oxygen intake was statistically signifilcant. The lower border of 95% confldence interval at the extreme value of maximal oxygen intake was calculated to be 41.475 ml/kg·min according to the quadratic regression equation of maximal oxygen intake of air temperature and standard error of estimated maximal oxygen intake from the regression. 41.475 ml/kg·min was confirrned to be correspondent with the estimated maximal oxygen intake at 24.2°C and that at 39.6°C. Therefore, the lower and upper critical temperatures formaximal oxygen intake in adult females were predicted to be 24.2°C and 39.6°C, respectively.

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Maximal oxygen uptakes (V_02max) of 26 female students, athletes(n=13) and nonathletes (n=13), were measured by progressive bicycle exercises in neutral (Ta : 25°C) and hot (Ta : 35°C) environments, Heart rate (HR), systoiic blood pressure (SBP) and rectal temperature (Tre) were recorded continously during exercise. V_02max of nonathletes were not significantly decreased in hot environment. On the other hand, athletes decreased siguificantly V_02max by 6.5% in hot environment. There was no difference between groups in maximal HR in neutral or hot environments. In neutral environment, SBP of athletes at maximum work loads were significantly higher than those of nonathletes, but in hot envirolllnent, there was no difference between groups. Tre of aihletes at maximum work loads were significantly higher than those of nonathletes in both enviroments due to long exercise time. But in both qroups, there was no difference of Tre between environments.

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The purpose of this study was to estimate the heat production rate for lean body mass and for fat tissue during acute cold exposure. Eight healthy young adults were investigated to determine their body composition by underwater weighing technique, basal metabolic rate and resting metabolic rate at air temperature of 13°C. There were no thin or obese men in the subjects (mean values of 12.3% in the fat content of body weight). Resting metabolic rate at the end of 90 minutes cold exposure was greater than basal metabolic rate by 31%. With use oflinear model of total heat production on two components of a body, heat production rate for fat tissue was calculated to be the proportion of 28% to total heat production in the basal state and to be very high under the cold environment. Though these results depended on the basis of calculation, fat tissue was supposed to have a trend of increase in metabolic activity during cold exposure.

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Cardiovascular responses during 30 min of exercise in 20°C, 30°C, and 40°C(R.H.50%) were measured in six male Japanese. The subjects exercised on a bicycle ergometer at the two kinds of work loads, i.e., 300 and 600kgm/min. Cardiac output(Q) was detennined with the CO₂ rebreathing method at the 5th, 15th, and 30th min of exercise. Oxygen uptake(V_O_2), heart rate(HR), rectal temperature(Tr), and mean skin temperature(Ts) were also measured. V_O_2 and Q did not change siguificantly during exercise in all environments. Analysis of variance showed that the factor of ambient temperature had no siguificant effects on V_O_2 and Q. HR increased with time and SV decreased with time during exercise. The largest change in HR and SV occured between the 5th min and the 15th min of exercise. Tr increased with time during exercise. The marked increase in Tr occured between the 15th min and 30th min of exercise. The regression equations of HR on Q and SV on Q in each time of exercise were calculated. The analysis of covariance showed that the elevation of regression line of HR on Q in the 5th min of exercise was significantly lower than those in the 15th min and the 30th min of exercise. Similarly, the elevation of regression line of SV on Q in the 5th min of exercise was significantly higher than those in the 15th min and the 30th min of exercise. From the regression equation of SV on Tr the adjusted values of SV for each time of exercise were calculated in order to exclude differences in Tr. The adjusted values of SV in the 5th min of exercise was siguificantly higher than those in the 15th min and the 30th min of exercise. So the alterations in HR and SV observed between the 5th min and the 15th min of exercise may accounted for by other than the change in internal body temperature.

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Nine healthy male students were exposed to heat for 61 minutes in summer. The therrnal conditions in a climatic chamber were 28°C, 36°C, 45°C and 50°C DB with 50%RH. Rectal temperature and mean skin temperature were measured on resting subjects during heat exposure. During exposure rectal temperatures decreased at 28°C, and increased at 45°C and 50°C. Rectal temperature at 36°C showed no definite tendency. Mean skin temperature increased at 36°C and 50°C. Close correlation was found between rates of increase in rectal temperature at 36°C and those at 45°C. Rates of increase in rectal temperature at 50°C correlated with those at 361C and those at 45°C . Rates of increase in rectal temperature at 36°C, 45°C and 50°C had negative correlations with weight, body surface area, lean body mass, % body fat and mean skinfold thickness, and had a positive correlation with body suface area / weight.

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The purpose of this study is to examine whether there is seasonal effects on the relationships between some morphological measurments and decrement of rectal temperature in a cold environment. Nine male subjects who wore thin shirts and shorts were exposed to 12iC with relative humidity of 50% for 60minutes. The experments were perforrned in Summer and in Winter. The relative large decrement of rectal temperature during the last 30 minutes of exposure to a cold air were observed only in relative lean subjects in Summer, but not in all in Winter. The decrement of rectal temperature was more affected in Summer by the variations of body fat per cent and body surface area per unit body volume. However, metabolic response to a cold air was more affected in Winter by the variations of the above two parameters. It was concluded that morphological factors were related intimately to heat loss by which rectal temperature was decreased in Summer and to heat production by which rectal temperature was maintained in Winter in a cold environment. Therefore, it was thought that an index as a cold tolerance such as lower critical temperature was more related to morphological factors in Winter than in Summer.

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Twelve male adults, aged 18-31 yr, exercised on a bicycle ergometer for 32 min at each of the two kinds of work loads, i.e., 300 and 600 kgm/min, in a warm environment (DBT=29.2± 1.44°C, WBT=22.8±2.05°C. Oxygen uptake (V_O_2) and increase in rectal temperature (ΔTr) were measured at the last of the exercise. The skinfold thicknesees were measured at six sites, i.e., triceps, chest, abdomen, iliac, subscapula, and thigh. Mean skinfold thickness (MSF), body density, body fat (Fat), Iean body mass (LBM) and body surface area (BSA) were calculated from the prediction equations. The multiple correlations for ΔTr, V_O_2, weight(wi) and MSF, and for ΔTr, V_O_2, Wt and Fat were found to be siguificant (R=0.874 and R=0.871), and the multiple regressions of ΔTr (°C) on V_O_2 (ml/min), Wt (kg) and MSF (mm), and on V_O_2, Wt and Fat (kg) Were calculated as, △Tr= 1.85+0.000661 VO₂-0.0418 Wt+0.0289 MSF, and ΔTr= 2.01+0.000658 V_O_2-0.0472 Wt+0.0568 Fat. These equations may indicate that the increase in body temperature is accelerated by the thick subcutaneous fat and/or by the rich adipose tissue.

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Five young male subjects with different individual VO₂max and similar fat % were examined their thermal and cardiovascular responses to work in water (27 and 31°C and air. During head out immersion, three subma:ximal work (VO₂ = 1, 1.5 and 2 1/min) for 30 min on a cycle ergo-meter were perforrned to examine the adaptability to cold in water compared to air. The sub-maximal VO₂ during light work in 27°C water was higher than that in 31°C water and air due to shivering. The bradycardia in colder water (27°C) shown during work was compensated by increased stroke volume since the Q during work was the same in air and water. The skin tempera-ture (Ts) in water was almost same as temperature of water and much lower than Ts in air. Despite the linear relationship between the rectal temperature (Tr) and VO₂ in air and water, Iower Tr in 27°C water was observed in a given VO₂ due to larger heat loss. Although the Tr-% VO₂max was linear both in air and water, the slope of the line in colder water was reduced. The present study suggests some interactions between aerobic and cardiovascular capacity on thermai balance in water although the precise relationship is still unknown.

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Physiological thermogenesis in intemal organs as well as main muscle groups is one of the most important subjects in the study of human adaptability to cold environment. The experiments of the prediction of obligatory non-shivering thermogenesis were performed under optimal thermal condition in summer and in winter by using a prediction method of local muscle energy metabolic rate and quasi-basal metabolic rate B₁ (Yokayama, 1980). B₁ means the sum of metabolic rates other than those of main muscle groups. The subjects were eleven Japanese males in sumrner and ten Japanese males in winter. Subject YS was longitudinally examined to confirm seasonal change of obligatory non-shivering thermogenesis. Subject YS was performed to examine regulatory non-shivering thermogenesis and shivering thermogene-sis by using nine resting and static exercising items of back cold and front cold under three cold environments (T=-l0°C, -5°C and 0°C. In the summer experiments Bls were 32.43 (mean) ±12.59 (S.D.) kcal/h and B₁/A= 19.81 ±9.26 kcal/m² h. On the other hand, the results of the winter experiments were 67.32±7.83 kcal/h and B₁/A=38.90±5.27 kcal/m³h. This tendency of the seasonal variation that the quasi-basal metabolic rate B₁ in winter was greater than in summer was coincident with the results in winter and in summer obtained from the same subject YS. In subject YS the predicted B₁S were 29.87 in summer, 57.84 in December and 55.55 and 57.92 kcal/h in March. In order to evaluate regulatory non-shivering thermogenesis, the predictions of B₁ were performed from item-e of back cold and front cold under cold environments. B1 under T=-5°C and T=0°C were 78.19 and 83.13 kcal/h respectively. Therefore the value of regulatory non-shivering thermogenesis was about 22 kcal/h under the present experimental conditions. The shivering thermogenesis was predicted for six to nine muscle groups in nine resting and exercising items of back cold and front cold under three cold environments

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