Sports drinks have been around for just over 50 years, and were invented at a US university as a pretty unappetizing solution of salt, sugar and water. It worked through, in that they improve performances by slowing down athletes rates of dehydration while providing an easily absorb energy boost. Today, like almost everything else connected with running, sports drinks have been scienced up, but, essentially not much has changed and they're still the mix of water, carbohydrates, and electrolytes.

For a distance runner, the main advantage of sports drinks over plain water is its carbohydrate content. In this form it will get into your system immediately and serve to quickly replenish your deplete glycogen levels. Also, the addition of carbohydrate speeds up your body's absorption of the drinks water element. However, for it to be of value to you, sports drinks carb content has to be between 5% and 8%. If it is much lower, it won't be enough to make any difference and you might as well save your money. If it is higher than 8% than the concentration of sugar will actually impede your body's water absorption, you will require too much of the energy that should be saved for running, to be used up breaking it down.

Types of sports drinks:

There are three types of sports drinks on the market:

Isotonic: balance of carbs and electrolytes to water is the same as in the human body, so it will be absorbed at around the same speed as water, but has greater calorific value.

Hypotonic: the carb and electrolyte/water ratio is less than the body's, so the fluid is absorbed quicker than water but with less energy replenishment.

Hypertonic: A greater carb/electrolyte concentration than the body, so the fluid is absorbed the slowest, but the energy replenishment is greatest. Best as an after race recovery drink.