Sports drinks containing electrolytes and carbohydrates are superior to water as a rehydration drink during moderate-intense exercise. These drinks contain sodium chloride and carbohydrates such as sucrose and glucose (maltodextrin). Gastric emptying improves whenever salts and carbohydrates are added to water, therefore improving its transport from the intestine to the blood compared to when drinking only water (1).
Carbohydrates obviously provide extra energy, especially when you are finishing your exercise. And certain athletes lose a large amount of salt through sweating and this salt has to be recovered if they are to remain hydrated. Apart from improving water absorption in the intestine, the salt in a sports drink stimulates thirst through the brain and minimises urine formation in the kidneys, thus improving the body's ability to retain body water (2).
Finally, whenever athletes warm up and start to sweat, they usually drink something more pleasant tasting than water (3). Glucose, sucrose, fructose, and maltodextrins (glucose polymer) are appropriate carbohydrates to make up a sports drink. Actually, as each carbohydrate enhances fluid absorption in the intestine through different pathways, having several types of carbohydrates in a rehydration drink may be beneficial (1).
MALTODEXTRIN: Several studies (4) recommend that maltodextrin can be used as an ergogenic aid to reduce fatigue and increase sports performance, since it promotes the recovery of muscle glycogen during and after exercise, increasing physical capacity, improving performance and preventing injuries in athletes, allowing a better recovery of energy reserves.
The administration of maltodextrin during high-load activity increases blood glucose concentrations, decreasing epinephrine concentrations, therefore reducing fatigue levels (5, 6).
SODIUM AND CHLORINE: (in the form of sodium chloride): A source of salt in sports drinks is critical, particularly during high sweating sports since water with sodium and chlorine (salt) is essentially lost through sweat (7). Furthermore, salt favours the isotonicity of the beverage and contributes significantly to preventing hyponatremia associated with exercise. Hyponatremia occurs whenever sodium levels in the blood plasma fall below certain limits (130 mM/L) and can lead to encephalopathy and pulmonary oedema depending on the degree.
POTASSIUM: While not to the same measures as sodium, plasma potassium levels tend to decrease during exercise (8). Potassium is essential for isotonicity, electrolyte balance, nerve transmission, and active transport mechanisms (7).