Many athletes cannot consume food before or during exercise and therefore a formulated drink that will provide carbohydrate is required. Electrolytes, especially sodium and potassium, in a drink will reduce urine output, enable the fluid to empty quickly from the stomach, promote absorption from the intestine and encourage fluid retention. Drinking plain water causes bloating, suppresses thirst and thus further drinking. It stimulates urine output and therefore is inefficiently retained. A poor choice where high fluid intake is required.
Water contains no carbohydrates or electrolytes.
There are three types of Sports drink all of which contain various levels of fluid, electrolytes and carbohydrate. The osmolality of a fluid is a measure of the number of particles in a solution. In a drink these particles will comprise of carbohydrate, electrolytes, sweeteners and preservatives. In blood plasma the particles will comprise of sodium, proteins and glucose. Hypotonic fluids have fewer particles than blood and Hypertonic have more particles than blood.