An athelete needs more energy when he runs inthe race which means he needs more oxygen. Therefore, in order to have more oxygen their rate of breathing increases and this speeds up the process of getting rid of carbon dioxide. Basically, the proces happens just to ensure that more oxygen is absorbed into the blood, and more carbon dioxide is removed from it. This is the reason, an athlete needs to breathe faster and deeper than usual; after finishing the race.Once normal levels are reached again their breathing returns to normal.