The primary purpose of drinking sports drinks rather than plain water is to maintain a sufficient concentration of blood glucose and to sustain a high rate of energy production from blood glucose and muscle glycogen. Sports drinks are mild carbohydrate-electrolyte solutions, designed to keep bodies well- hydrated and fueled during exercise of longer than 45 minutes. Drinking fluids during exercise also reduces the increase in body temperature and the amount of stress on the cardiovascular system, especially important when exercising in hot environments.
Generally, sports drinks offer approximately 14-20 grams of carbohydrate per 250 ml (8 ounces). This carbohydrate level is approximately 6-8 % carbohydrate in solution, delivers the optimal amount of both energy and fluid to enhance performance during exercise. The carbohydrates can come in many different forms: sucrose, glucose, fructose and glucose polymers. Those sports drinks that contain mostly fructose may slow absorption down and cause stomach cramps because fructose is absorbed by passive diffusion in the gut.