In a recent issue of Medicine and Science Sports and Exercise, the American College of Sports Medicine published an official position stand on hydration and exercise.
How much is enough? How often? What kind of drink is appropriate?
After reviewing almost 100 scientific experiments involving exercise and the maintenance of essential body fluids, a panel of specialists came to the following conclusions and recommendations:
Eat a nutritionally complete diet and match this with adequate fluid intake during the day before you exercise or compete in an athletic event. The committee emphasized that adequate fluids to accompany the meal consumed closest to exercise are the most important.
Drink approximately two 8-ounce glasses of fluid 2 hours before exercise. A tactful distinction was made between a 2-hour vs. 1-hour time span. A full 2 hours will allow proper hydration and elimination of unnecessary fluid. In other words, you don’t want your exercise bout interrupted by constant trips to the restroom.
While exercising, drink early and often. How much? Enough to balance the water lost by evaporation of sweat or as much as can be comfortably “tolerated.” Remember, your thirst mechanism is not a good indicator of how soon to drink, and by that time your body is dehydrated.
The temperature of your drink should be cooler than the surrounding environment. The ACSM panel recommends 59 to 72 degrees Fahrenheit. Additionally, flavored fluids may enhance the taste of a drink. A little psychology here: if you like it, you are likely to drink more of it.
If you are exercising longer than 1 hour, you should consider a fluid with added carbohydrates and electrolytes. Minimal research has been done on exercise bouts shorter than 1 hour, so ACSM recommends only water consumption for this type of brief physical activity.
How much of your drink should be composed of carbohydrates? During physical activity that is maintained for more than 1 hour, “carbohydrates should be ingested at a rate of 30-60 grams/hour.” If you are drinking 600-1,200 milliliters per hour, this fluid should be 4-8 percent carbohydrates. The panel concluded that the form of carbohydrates, i.e. glucose, sucrose or starch, made no difference. They did note that fructose should be avoided as it may cause stomach and intestinal pain.
Similarly, during an exercise bout that will extend beyond 1 hour, electrolyte replacement is recommended. Sodium or NaCl is the most common. Notice the recommended amount is at 0.5-0.7 grams per liter of water. Read the labels carefully on sports drinks because sodium content is usually expressed in mg or milligrams not grams. 1 g equals 1000 mg. Therefore you are looking for a drink with 500-700 milligrams per liter.
Well-educated coaches, trainers and fitness professionals have been making similar but probably not as specific suggestions for years. However, if you’re wondering if the water most of us prefer or your sports drinks are most effective, read the label and see how yours stack up.