Final answer:
Drinking water during training helps athletes tolerate heat by using it as a heat sink and through the evaporation of sweat, which cools the body. In humid conditions, staying hydrated becomes even more important as the evaporation rate decreases.
Step-by-step explanation:
Water consumption during training enables an athlete to better tolerate the heat. This is because the body uses water as a heat sink, where it absorbs the heat generated by chemical reactions during physical activity without a significant increase in temperature. Additionally, to prevent overheating, the body sweats, and as the sweat evaporates from the skin, it takes with it a large amount of heat, thereby cooling the body. However, in high humidity, the air is saturated with water vapor, reducing the rate of sweat evaporation and, consequently, the cooling effect. Therefore, it's crucial for athletes to stay hydrated, especially in humid conditions, to maintain the body's ability to regulate its temperature efficiently.