Water, body's main transportation mechanism, takes nutrients, waste metabolites and internal secretions (for example, hormones) to target tissues; it
also regulates body temperature by removing heat from working muscles and routing it to the skin to cool the body through evaporation of sweat.
Everyone requires a minimum of 2 quarts of water a day, and even the smallest deficit can leave you feeling tired (dehydration is a common cause of
fatigue) or ill.
Water is crucial to athletes, especially under hot and humid conditions. Hard training in such weather can easily lead to a 2-quart loss of water, which results in an approximate 10% decrease in exercise performance. This is about the point where you begin to feel thirsty. Sweating buckets can impair your concentration and reaction time, so if you feel too tired after your workout to think, drink up.
At a certain threshold of dehydration, when the body urgently needs water, nothing else can substitute. Drinking tea, coffee or cola can over stimulate your central nervous system with caffeine and, at the same time dehydrate your body because of the strong diuretic action on the kidneys, which causes increased urine production. Plain water doesn't contain sugar, caffeine or other compounds that could alter the mind and body.
You've already become a little dehydrated by the time you feel thirsty, so keep a bottle of cool water handy to sip from throughout the day. For proper fluid hydration during exercise, follow these recommendations:
Drink 2-3 cups of water two hours before exercising
Consume 2-3 cups of water 10-15 minutes before exercise
Drink 1 cup of water every 15 minutes during exercise
Weigh yourself before and after exercise, then drink 2 cups of water after exercise for each pound of bodyweight lost