Circadian variation of thermoregulatory responses during rest in water / 体力科学

ABSTRACT

To observe possible influences of the biological clock on thermoregulatory responses, heat balance was measured 6 healthy students wearing only trunks during 30 min of immersion in water at a temperature of 21°C in both the rising phase (11 00-13 00) and the falling phase (23 00-1 00) of body temperature.<BR>Heat production was higher in the rising phase than in the falling phase. Duration of shivering was longer in the rising phase than in the falling phase. Dry heat loss was nearly constant, 163 to 166 W/m<SUP>2</SUP> in both phases. Body heat storage was negative in both phases, but higher in the falling phase than in the rising phase.<BR>The mean body temperature, however, changed to a similar extent in the rising phase and in the falling phase when the circadian temperature variation was balanced.<BR>Analysis of these results implies that the increased shivering in the rising phase is brought about by changes in the sensitivity of the thermoregulatory response.