ABSTRACT
Introduction: We examined the thermophysiological effects of ultrafine bubble (UB) bathing in comparison with microbubble (MB) and freshwater (FW) bathing. Subjects and Methods: Seven healthy women aged 35.6±2.9 years provided informed consent to participate in the study. After a 10-min rest, each subject engaged in UB, MB, and FW bathing (on separate days) at 40°C for 10 min. During the experiment, tympanic temperature, local sweat rate, local skin temperature, heat flow, and heart rate variability were continuously recorded. Subjective assessments of thermal sensation and comfort were rated on a visual analog scale between 0 to 100. Results: Increases in tympanic temperature and mean body temperature were highest during MB bathing, and similar increases were observed during UB and FW bathing. Local sweating was highest during MB bathing and lowest during UB bathing. A significant interaction was observed between local sweating during bathing and bathing style (P<0.001). The increase in local sweat rate relative to body temperature was lowest during UB bathing and highest during MB bathing. Discussion: During UB bathing, UBs and MBs that were generated in high concentrations in the bathtub decreased the flow of heat to the body, thereby suppressing an increase in tympanic temperature and yielding the lowest local sweat late. However, during MB bathing, in which a moderate concentration of UBs and MBs were generated, the increase in heat flow due to the convection of hot water exceeded the decrease in heat flow due to the bubbles. Conclusions: The results suggest that bubble properties and convection characteristics altered the balance of heat flow, leading to differences in the thermoregulatory response during and after bathing.
ABSTRACT
Introduction: We examined the thermophysiological effects of ultrafine bubble (UB) bathing in comparison with microbubble (MB) and freshwater (FW) bathing. Subjects and Methods: Seven healthy women aged 35.6±2.9 years provided informed consent to participate in the study. After a 10-min rest, each subject engaged in UB, MB, and FW bathing (on separate days) at 40°C for 10 min. During the experiment, tympanic temperature, local sweat rate, local skin temperature, heat flow, and heart rate variability were continuously recorded. Subjective assessments of thermal sensation and comfort were rated on a visual analog scale between 0 to 100. Results: Increases in tympanic temperature and mean body temperature were highest during MB bathing, and similar increases were observed during UB and FW bathing. Local sweating was highest during MB bathing and lowest during UB bathing. A significant interaction was observed between local sweating during bathing and bathing style (P<0.001). The increase in local sweat rate relative to body temperature was lowest during UB bathing and highest during MB bathing. Discussion: During UB bathing, UBs and MBs that were generated in high concentrations in the bathtub decreased the flow of heat to the body, thereby suppressing an increase in tympanic temperature and yielding the lowest local sweat late. However, during MB bathing, in which a moderate concentration of UBs and MBs were generated, the increase in heat flow due to the convection of hot water exceeded the decrease in heat flow due to the bubbles. Conclusions: The results suggest that bubble properties and convection characteristics altered the balance of heat flow, leading to differences in the thermoregulatory response during and after bathing.
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.