Whenever body temperature rises, as in intense exercise, the sweating mechanism is one of several ways to cool the body. When you sweat, you lose water, electrolytes such as sodium, potassium, chloride, and small amounts of other vitamins and minerals. In order to maintain peak performance, these losses have to be replaced. Even relatively mild degrees of dehydration of as little as 1-2% of body weight can result in serious impairments in athletic performance.

The decision to drink water or a sport drink used to be more a matter of personal preference and taste than anything else. There is little doubt that 16 ounces of water will rehydrate you just as effectively as the same amount of a sports drink. The difference between the two, however, comes down to whether the demands of your activity require the replacement of other things as well. Long duration exercise in the heat may be aided by provision of carbohydrates and electrolytes along with the rehydrating fluid. There is also some evidence that certain electrolyte mixtures promote faster absorption of the fluid from the stomach than pure water. Cool fluid will empty faster than a room temperature beverage and will provide the added benefit of cooling the body if exercise is performed in a hot environment.All exercises require adequate replacement of body fluids lost through perspiration.