抄録
Many studies on long-term head-down bed rest (HDBR) used as a simulation of microgravity indicate that sweating response is reduced accompanying an elevation of core temperature, suggesting that the alteration of sweating response during HDBR may be caused by the dehydration induced. This study was aimed to investigate whether the reduced sweating response is prevented by HDBR in the absence of dehydration. In 12 healthy male volunteers, daily water intake was encouraged during 20 days HDBR to match the urine volume in the previous day. Six of twelve subjects exercised every day during HDBR. Before and after the session of HDBR, each subject was immersed his legs in hot water at 42 o C for 45 min in a sitting position. Core (tympanic) temperature, skin temperature, chest sweat rates and chest blood flow were recorded continuously. Body weight was not significantly changed after HDBR for each of the exercise and the control groups. Higher core temperatures and blood flow, greater sweat rate, and earlier onset of sweating were observed during the hot water immersion after HDBR. The regression line relating sweat rate to body temperature was not significantly shifted after HDBR in both of the exercise and the control groups, indicating that sweating function was not altered by the HDBR. It was concluded that encouraged water intake (i.e., euhydration) can prevent the reduced sweating response under microgravity condition such as during spaceflight. [J Physiol Sci. 2007;57 Suppl:S178]
