Effect of passive heating for 14 days on thermoregulatory responses and subjective thermal sensation in humans

Abstract

We investigated the effect of passive heating on thermoregulatory responses and subjective sensation. Six volunteers were subjected for the experiment at latitude 35°N; in which the mean temperature and hours of daylight were 7.3°C and 11:21 hours in winter. Subjects entered a climatic chamber at 40°C and 50%RH for 90 min for 14 days. Core and skin temperatures, sweat rate and cutaneous blood flow were measured during leg water immersion at 42°C for 30 min in pre‐, 7th and post‐passive heating session in 26°C and 50%RH. Subjective thermal sensation was asked every 5 min during water immersion. Antidiuretic hormone (ADH), angiotensin II, aldosterone, and total proteins were measured in the immersion days. Tympanic temperature, sweat rate and cutaneous blood flow during water immersion were not significantly different between pre‐ and post‐passive heating session. The concentration of ADH, angiotensin II and aldosterone were not significantly different between pre‐ and post‐passive heating session. Thermal sensation rating was significantly lower in post‐ than in pre‐passive heating. These results suggested that subjective thermal sensation might be changed after 14 days passive heating at 40°C and 50%RH without changes in core temperature.