The quicker enduance athletes replenish their body liquids after training in hot weather, the quicker they recover. The best way of doing this is through complete foods eaten in the form of a full meal, says sports scientist Rick Sharp of Iowa University in a review study that was published in the Journal of the American College of Nutrition.
If you haven’t lost too much liquid, then water is the best way to replace it. But if you’ve lost a lot of body fluid, you probably won’t be able to drink enough water. You drink more of a liquid that has a flavour added to it, and even more if it also contains some glucose and salt. The figure below shows how much young men drank after doing endurance sports for three hours in an ambient temperature of 35 degrees. They only managed to replenish their fluid reserves when they drank the beverage represented in the right-hand column.
But even if you add electrolytes and sugars to drinks, the liquid you put back into the body is lost again quickly via the urine. If you take in liquid in the form of water accompanied by a meal, you lose the liquid less quickly. The figure below shows this. The graph refers to adults who had first lost two percent of their bodyweight in the form of liquid and then replenished this either with sports drinks or with a meal and extra water. The curves show the volume of urine.
Both the sports drinks and the meal replaced the lost body fluid equally fast, but as the graph below shows, the effect of the drink was more short lived than that of the meal.
Losing body fluids is not just a question of water loss, Sharp concludes. To make sure the cells in your body get enough water you obviously need more substances than just water – and more than just the electrolytes and sugars in sports drinks.
J Am Coll Nutr. 2007 Oct;26(5 Suppl):592S-596S.