Hydration in sport and exercise: water, sports drinks and other drinks

There is evidence to suggest that exercise-induced dehydration can have a negative impact on exercise performance, and restoration of fluid balance should be achieved after exercise. It is equally well known that muscle glycogen must be restored after exercise if subsequent performance is not to be negatively affected. Sports drinks are ideally placed to fill both these roles. However, while muscle glycogen restoration can be comfortably achieved by consumption of solid food, the same is not true for restoration of hydration status. Clear evidence is available that drinking during exercise can improve performance, provided that the exercise is of sufficient duration for the drink to be emptied from the stomach and absorbed in the intestine. Generally, drinking plain water is better than drinking nothing, but drinking a properly formulated carbohydrate-electrolyte 'sports' drink can allow for even better exercise performance. Of importance for rehydration purposes after exercise is consumption of both an adequate volume of fluid (greater than the net deficit of the sweat volume lost) and quantity of sodium. Without both of these, rehydration will be neither rapid nor complete and maintained. There is, however, no good evidence for the inclusion of any other electrolytes. The current generation of commercially available sports drinks are generally formulated to meet the needs of many athletes in many different situations.