6.3 Sports drinks
If an individual is appropriately fuelled, water may be adequate for activities of less than one hour. In addition to water, there are three types of sports drink which can be used for a combination of hydration and energy replacement: hypotonic, hypertonic and isotonic.
Hypotonic sports drinks
For events of a long duration, hypotonic sports drinks which supply some carbohydrate may be preferred to water. They have a lower concentration of particles than body fluids (less than 4 g carbohydrate per 100ml); meaning that they are absorbed into the body more quickly than water. Hypotonic sports drinks also contain the electrolytes sodium and potassium, which control the flow of water in and out of cells and are vital to ensure absorption.
Hypertonic sports drinks
Hypertonic sports drinks contain more than 8 g of carbohydrate per 100 ml.They increase the amount of carbohydrate fuel that can be supplied to the muscles, but that will also decrease the rate at which water is available because it slows the rate at which the contents of the stomach empties into the small intestine.
Isotonic sports drinks
Isotonic sports drinks have the same concentration of dissolved particles as body fluids (5–7 g carbohydrate per 100 ml). They are a good choice because they contribute to the carbohydrate needed post-exercise. They also contain the electrolytes, sodium and potassium. They are considered beneficial for use by athletes for events of one hour or more in duration.These drinks are beneficial for endurance sports because they provide a source of fuel (usually glucose sucrose, glucose polymer or maltodextrin) in addition to water to reduce dehydration. Isotonic drinks are absorbed as fast as, or faster than, water alone.
The decision to use hypotonic, hypertonic or isotonic drinks will depend on whether the athlete’s goal is to promote hydration, carbohydrate uptake or a balance of both.