HERSHEY, PA. — Anyone who exercises even moderately in hot weather should be advised to drink more than water—something with salt and sugar—to replenish the carbohydrates and electrolytes that the body sweats out in order to avoid potentially life-threatening complications from a heat-related illness.
Remember that all-cause mortality from cardiac disease increases in hot weather, said Dr. Eric E. Coris at the annual meeting of the American Orthopaedic Society for Sports Medicine.
As the body heats up and dehydrates, less oxygen reaches the muscles, which causes muscle cramping. Dehydration also decreases blood volume, impairs gastric emptying, and hinders the flow of blood to the kidneys and other organs, said Dr. Coris, director of the Sports Medicine Institute at the University of South Florida, Tampa.
The presence of sodium in water or another beverage, such as lemonade or a sports drink, improves the body's ability to absorb fluids.
Although water alone is sufficient to rehydrate most athletes during events that last less than an hour, drinking something with carbohydrates prior to the event can help prevent dehydration in hot weather, Dr. Coris said. For events lasting an hour or longer, he recommends plain water before the event, followed by a solution with both sugar and salt during the event to maintain the carbohydrate and electrolyte balance and prevent hyponatremia.
The ideal sports drink for most activities contains 400–800 mg/L of sodium, with some sugar, in the form of 30–80 g/L of carbohydrates, and most commercial sports drinks meet these criteria, said Dr. Coris, who has no financial interest in any sports drink manufacturers.
“Athletes drink more of any beverage when there is sugar in it,” he said. But avoid denser drinks, such as orange juice, because too much sugar could cause stomach cramps, he emphasized. Standard sports drinks provide enough sodium for mild to moderate activities, but athletes who do long or intense workouts in hot weather may need even more sodium than sports drinks provide.
Even highly conditioned athletes can overheat in extreme conditions and find themselves dehydrated. Runners, for example, may sweat about 1.5 L/hr on a hot day, and most people can easily replace only 0.75 L/hr, Dr. Coris said.
“Football is one of the monsters of fluid loss,” he added. College football players have been known to lose 3–4 L of fluid during twice-daily practice regimens in August. For these athletes, a standard sports drink probably does not provide enough sodium. Adding one teaspoon of salt to a 32-ounce bottle of sports drink and drinking it slowly after the event is an effective way to rehydrate, he noted.