Drink plenty of cool plain water before, during and after training and competition, even if you do not feel thirsty.
Drink 1-1 1/2 cups of water 15 minutes before training or competition.
Drink 1/2 cup every 20-30 minutes during the event.
Don't rely on thirst as a guide to how much water your body needs. Weigh yourself before and after exercising. For every pound lost as sweat, drink 2 cups of water.
Remember that water is a key nutrient for athletes, it helps to regulate body temperature, to carry nutrients and oxygen to the cells and in the excretion of the waste products of metabolism.
Avoid salt tablets. Too much salt draws water into your stomach to dissolve and dilute it, which adds to dehydration. Salt tablets can also act as an irritant to the stomach and cause nausea and vomiting.
Sweat is really very dilute. Electrolyte lost through sweat can usually be replaced adequately with regular foods.
Full strength sports drinks do not provide enough plain water by them selves.
If sport drinks are used, either dilute them or make sure you are drinking an equal amount of plain water.
The ratio of Carbohydrates to Proteins and Fats also affects the bodies ability to hold water or excrete it. Make sure you eat enough of all of the components of foods to keep a healthy balance.