Experimental study on the variations in human skin temperature under simulated weightlessness

To study the variations in skin temperature in weightlessness, the skin temperatures of 6 male volunteers were measured under simulated weightlessness by head down bed rest (HDBR) experiments. The effects of the air temperature, relative humidity and air speed on the mean skin temperature were scrutinized, and the regional skin temperatures of the subjects under comfortable conditions were investigated. The results showed that the mean skin temperature increased with the air temperature both before and after HDBR in low and neutral air temperatures and that the mean skin temperature was found to be higher before HDBR. However, a higher mean skin temperature was observed after HDBR when the air temperature was high. Moreover, the mean skin temperature in low and neutral air temperatures was found to increase with the relative humidity both before and after HDBR, and a higher mean skin temperature was also observed before HDBR. Additionally, a negative correlation between the mean skin temperature and air speed was observed both before and after HDBR. However, different patterns of the mean skin temperature were observed when the environment changed from low air temperature and humidity to a neutral environment and finally to a high air temperature and humidity. Finally, the regional skin temperature after HDBR showed a different distribution compared with that before HDBR, such as a higher skin temperature in the thorax, forehead and back and a lower skin temperature in the thigh, calf and hand. This indicated that the skin temperature distribution changed greatly under simulated weightlessness by HDBR, which might suggest an altered thermal regulatory mechanism in humans experiencing weightlessness.