From Nancy Clarks Sports Nutrition Guidebook by Nancy Clark, MS, RD
What should you drink during exercise? The recommended fluid replacer contains a little sodium to stimulate thirst, a little potassium to help replace sweat losses, and a little carbohydrate (sugar) to provide energy. More precisely, the drink should contain 110 to 170 milligrams of sodium per 8 ounces (20 to 30 milliequivalents (mEq) sodium/L); 20 to 50 milligrams of potassium per 8 ounces (2 to 5 mEq potassium/L); and about 12 to 24 grams of carbohydrate per 8 ounces (in a 5 to 10 percent sugar solution, for 50 to 95 calories) (ACSM 2007). You can consume these nutrients via standard foods such as pretzels and bananas as well as engineered foods (see chapter 11), which can be more convenient for runners, triathletes, and other endurance athletes.
When you are exercising hard for more than an hour (or doing less intense, longer exercise), consuming 120 to 240 calories of carbohydrate (30 to 60 g) per hour along with your water can help you perform better. Carbohydrate helps maintain normal blood glucose levels so you are able to enjoy sustained energy. Sports drinks are an easy way to get carbohydrate plus water. For example, 16 ounces (480 ml) of Gatorade offers 25 grams of carbohydrate and 100 calories; 16 ounces of Powerade offers 35 grams of carbohydrate and 140 calories. Practice drinking appropriate amounts of fluid during training to help you adapt to the fluid load and prevent stomach sloshing and discomfort during competition.
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