It is an important part of weight management and stress reduction. Exercise develops muscle, which requires fuel for contraction and relaxation. Water transports the nutrients and waste products throughout the body. Heat produced by the body during exercise is controlled by sweating and your body temperature is regulated by the amount of water in your system.
Water is lost through perspiration and breathing.
Exercise in humid weather may create a sweat loss of 32 to 50 ounces a day. A great loss of fluid from the body may threaten cardiovascular function, cause gastrointestinal cramping and reduce physical endurance. Don't rely on your thirst mechanism to let you know when to drink. Exercise will dull the sensation for thirst. A more accurate measurement for fluid need is body weight.