For the proper performance of an athlete, the most important thing is staying hydration. An athlete must take water depending on his/her body weight, external temperature and body activity. So, the water requirement differs for athletes depending on their body weight and the external temperature. In general, the half of the weight of the athlete is taken into account and one ounce of water is taken per each pound of the athlete's weight. Even though athletes take fluids to replace the lost water, complete replacement of body water lost cannot take place. About 50 % of body water is hardly replaced, even though replacement fluids are given to athletes.