ABSTRACT

　Water molecule dynamics in vivo are important for heat stroke caused by exercise in high-temperature environments and its prevention. Water molecules in skeletal muscle and other living tissues can be broadly classified into “free water,” which can move freely without binding to other substances, and “bound water,” which is bound to other substances and whose molecular motion is constrained. However, the effects of hydration at the onset of heat stroke and afterward on water molecules of different properties, such as free water and bound water, are unclear. The present study examined the effects of running exercise-induced heat stroke caused in a hightemperature environment and subsequent hydration on water molecule properties and water transport mechanisms in skeletal muscle in rats. Running exercise at a running speed of 10 m/min was performed in a room maintained at a room temperature of 31±2ﾟ and humidity of 45±5%. The exercise was terminated when the rats lost 3% of their body weight during the running exercise. Hydration was then provided ad libitum for 24 hours. As a result, it was demonstrated that muscle water content changes in response to changes in free water volume due to running exercise-induced heat stroke and subsequent hydration. On the other hand, there was no change in hyaluronan concentration, suggesting that changes in bound water may not be affected. Furthermore, no significant changes were observed in the expression levels of AQP1 and AQP4, which are water molecule transport mechanisms. In the present study, it was suggested that running exercise induced heat stroke and subsequent hydration may affect the dynamics of free water, but not bound water. In addition, it was also indicated that the water molecule transport mechanism was hardly affected.　

DECENTE SPORTS SCIENCE Vol.46/The DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE