ABSTRACT
To clarify the effect of sports wear on exercise-heat stress, we analyzed quantitative differences in thermoregulatory responses among baseball uniforms (BB), soccer uniforms (SC), and swimming trunks (NU) during exercise in a hot environment. Eight male subjects performed three sessions of 20-min cycling at light intensity (250W/m<SUP>2</SUP>) wearing BB, SC and NU in a room maintained at 28°C (wet-bulb globe temperatures, WBGT) . Esophageal (Tes), mean skin (Tsk), and mean body temperatures (Tb), heart rate (HR), thermal sensation (TS), and total sweat loss (<I>m</I><SUB>SW</SUB>) were measured during the exercise. Increases in Tes, Tsk, Tb, HR, and TS during exercise were significantly (p<0, 05) higher, and <I>m</I><SUB>SW</SUB>, was significantly (p<0.001) greater for BB than SC and NU. The increase in Tes at the end of the exercise was 3.0 times higher for BB than NU ; and also 2.0 times higher for SU than NU. Under all conditions, the increase in Tes significantly correlated with Tsk (r=0.634, p<0, 001) and HR (r=0.854, p<0.001) ; <I>m</I><SUB>SW</SUB> also significantly correlated with Tb (r=0.683, p<0.001) at the end of the exercise. These findings suggest that quantitative differences regarding the increase in Tes among BB, SC and NU relate to Tsk elevation due to attenuation of heat dissipation depending on sports wear ; body temperature elevation also relates to the increase in HR and <I>m</I><SUB>SW</SUB> during light exercise in a hot environment.
ABSTRACT
Sensory estimates of thermal sensation of exercising unclothed five healthy male subjects have been compared with the associated thermo-physiological responses at various ambient temperatures.<BR>The subjects were exercising at approximately 50% of their maximal oxygen intake 30 minutes in a handmade wind tunnel. Three levels of ambient air temperatures were used at about 20°C, 25°C, and 30°C. Relative humidity was always maintained at about 60%, and the air movement was kept constant at 0.1 m/sec.<BR>Physiological measurements were thermal sensation, skin temperatures (22 points), rectal temperature, local sweating rate and total sweating rate.<BR>The relationship between rectal temperature and mean skin temperature and the estimate of thermal sensation was described by a summation model, where the thermal sensation was linearly related to the rectal temperature and the higher levels of mean skin temperature shifted the former relation to the higher deretion.<BR>The subjective estimate of thermal sensation (Sense) during exercise has been described as a summation of thermal signals from the core (Tr : rectal temperature) and the skin (Ts ; mean skin temperature) as follows ;<BR>Sense=2.21 Tr+0.29 Ts-84.81 (r=0.869, p<0.001)<BR>Further, the linear thermal sensation-rectal temperature relationship was dependent on ambient air temperature during exercise.<BR>Increasing the maximal oxygen intake decreased the gain of the thermal sensationrectal temperature relationship at only 30°C air temperature.<BR>It was difficult to estimate the local sweating rate by the degree of thermal sensation during exercise.
ABSTRACT
The purpose of this study was to investigate the possible individual difference in temperature regulating ability during identical relative exercise load under various temperature environments.<BR>Seven healthy males, aged 21 to 26 years, performed bicycle ergometer exercise of 60% VO<SUB>2</SUB>max for 60 minutes. All exercises were carried out in a climatic chamber under the conditions of 15°C (RH=70%), 25°C (RH=55%) or 35°C (RH=45%) . Herat rate, O<SUB>2</SUB> consumption, pulmonary ventilation, rectal temperature, mean skin temperature, local sweat rate at the lower part of scapula and total sweat rate were determined intermittently through the experiments. Moreover, heat loss by evaporation, radiation, convection and effective sweat rate was calculated using the heat valance equations.<BR>The results obtained are as follows :<BR>1. The increase in rectal temperature at the end of exercise was almost identical in 15°C and 25°C but significantly higher in 35°C.<BR>2. A significant positive correlation was observed between mean skin temperature (ΔTsk) at the end of exercise and effective sweat rate (r=0.468, p<0.05) during exercise.<BR>3. Inspite of the equality of relative exercise intensity (60%VO<SUB>2</SUB>max), marked individual variations were observed in rectal temperature during exercise.<BR>4. The subjects who showed marked increase in rectal temperature during exercise showed less marked increase in mean skin temperature in 15°C and 25°C and less marked increase in local sweat rate in 35°C than other subjects.<BR>It would be concluded that the main cause of individual variation in rectal temperature during exercise depends on difference in evaporative heat loss in hot environment and difference in skin temperature in mild or cold environment.