Look for three things: type of carbohydrate, amount of carbohydrate, amount of sodium.

Type of carbohydrate: You'll find some mixture of either simple sugars -- such as sucrose, glucose, or fructose -- or complex ones such as maltodextrin, or glucose polymers. Note that fructose takes longer to absorb and can cause nausea in some people. Maltodextrin and glucose polymers have been scientifically formulated and have proved to be absorbed more quickly. That makes their appearance on the label a good thing.

Amount of carbohydrate: More is definitely not better. For the most benefit, your sports drink should contain about 6- to 7-percent carbohydrate. For comparison, soda and fruit juice contain about 10- to 15-percent carbohydrate.

Math not your strong suit? Calculate that by dividing the grams of carbohydrates per serving by the number of milliliters per serving (eight ounces has 236 milliliters). For example, eight ounces of one drink has 14 grams of carbohydrate. Divide 14 by 236 milliliters. That gives you 6 percent. So shoot for between 14 and 16 or 17 grams of carbohydrates per eight ounces.

A higher carbohydrate concentration slows the transfer of water through your intestines into your system. All that expensive, carb-rich liquid ends up slooshing around in your stomach and intestines with nowhere to go, leaving your heart and circulatory system working harder than ever.

Amount of sodium: You can't completely replace your body's lost fluids until you replace the sodium lost. That's why sports drinks with a little sodium give you an extra boost. In one study from the University of Texas, dehydrated exercisers drank either water or a sports drink with sodium. The group that quaffed a sports drink retained more fluid that the group that drank plain water. Researchers concluded sodium enhances fluid absorption in the intestine. Look for about 50 to 120 milligrams of sodium per serving.