In order to store each gram of glycogen, the body has to store 2.7gms of water. It is possible to consider yourself optimally hydrated when you urinate frequently and your urine is clear. During performance take all the plain water you can get. This is particularly important for events of 30 minutes and over. Ideally water intake should match sweat loss and a prehydrated athlete has more water to spare, meaning better times and improved recovery.
Cold water leaves the stomach far more quickly than room temperature water.
Sip, don t gulp and stay away from the carbonated drinks that slow absorption. The single most important factor that affects the rate of water emptying is its glucose content. The more glucose present, the slower the gastric emptying time. This includes commercial sports drinks containing high levels of simple sugar don t be fooled by the false feeling of increased energy. For events of 1.5 to 2 hours or longer some additional glucose and electrolyte support may be beneficial.