Fluid Intake After Exercise

Athletes who have exercised intensely for an hour or longer are likely to experience some degree of underhydration. For those athletes who exercise most days (i.e., most elite athletes), postexercise fluid consumption becomes a critically important part of the exercise regimen because it helps the athlete begin each subsequent day of activity in a well-hydrated state. The important point to consider is this: It takes time to dehydrate. The less time there is to dehydrate, the lower the likelihood that the athlete will be optimally hydrated by the beginning of the next exercise session.

Athletes rarely consume fluids during exercise at a rate of more than 70 percent of sweat loss, and most athletes replace sweat losses at a rate significantly lower than this.^{84, 85} Therefore, most athletes require strategies to achieve adequate hydration before the next exercise session begins. Despite this clear need for fluids, athletes often remain underhydrated even when fluids are readily available to them.⁸⁶ This voluntary dehydration suggests that athletes should be placed on a fixed fluid-replacement schedule that will increase the likelihood of maintaining hydration. A way of encouraging this is to make certain that cool, good-tasting fluids are easily available to the athlete as soon as the exercise session is over.⁸⁷

Commercial sports drinks containing both carbohydrate and sodium are more effective than plain water at restoring water balance.⁸⁸ To maximize dehydration, however, it appears that a level of sodium greater than that provided in most sports drinks is desirable.⁸⁹ This added sodium can be obtained through the normal consumption of foods, many of which have added salt (sodium).⁹⁰

In general, athletes should follow these rules for fluid consumption after exercise:

1. A large volume of fluid (as much as can be tolerated, perhaps .5 liter) should be consumed immediately after exercise. This large fluid volume enlarges the stomach and increases the rate at which fluids leave the stomach and enter the small intestine to be absorbed.
2. After the initial consumption of a large fluid volume, athletes should consume approximately 1/4 liter of fluid every 15 minutes to achieve a fluid intake of approximately 3 liters of fluid in 3 hours. The larger the athlete and the greater the sweat loss experienced during activity, the greater the amount of fluid that must be consumed.
3. Fluids should contain both carbohydrate and sodium because both are useful in returning the athlete to a well-hydrated state. In addition, the carbohydrate content of the beverage helps in returning stored glycogen (energy) to muscles in preparation for the next exercise session.
4. Sports drinks typically provide approximately 10 to 25 millimoles of electrolytes (mainly sodium) per liter of fluid. However, the optimal sodium concentration for fluid retention is approximately 50 millimoles of electrolytes per liter of fluid.⁹¹ Since adding more sodium to fluids may make the fluid unpalatable and cause the athlete to consume less fluid, the athlete should be encouraged to consume some salted snacks (such as pretzels or saltine crackers) during the period immediately after exercise.
5. The loss in body weight that results from exercise should be the key to determining the total amount of fluid that must be replaced before the next exercise session. As a general guide, 1 pint (16 ounces) of retained fluid is equal to 1 pound of body weight. Since not all consumed water is retained, twice as much fluid may need to be consumed to replace the fluid equivalent in weight loss.
6. Fluids containing caffeine and related substances (coffee, tea, colas, chocolate) should be avoided because they increase urinary water loss.