Considerable interest is attracted to the problems on water ingestion during exercise, however, it is still hypothesis that water ingestion would attenuate the exercise-induced increase in thermoregulatory mechanism such as rectal and muscle temperatures and plasma epinephrine, thereby resulting in less net muscle glycogen utilization. In the present review article, therefore, the hypothesis was discussed and confirmed by the results of 25 important papers related to the problems of improvement of physical performance based on the following three papers : (1) Effects of fluid ingestion during intermittent high intensity swimming exercise on thermoregulatory response and performance. (2) Effect of fluid ingestion on muscle metabolism during prolonged exercise. (3) Heat stress increases muscle glycogen use but reduces the oxidation of ingested carbohydrates during exercise. These review articles indicate that fluid ingestions reduces muscle glycogen use during prolonged exercise, which may account in part, for the improved performance in the hypothesis mentioned above
