Adequate hydration is as important to good athletic performance as the food you eat. In cycling, rapid skin evaporation decreases the sense of perspiring and gives a false sense of minimal fluid loss (even though you are losing 2 quarts of fluids per hour).
Proper nutrition is fundamental to fitness and performance. Although many athletes carefully regulate their diet, they may pay little attention to their body’s fluid needs. They often misunderstand and underplay the importance of water to good nutrition.