Water is an essential nutrient and constitutes more than two-thirds of the body's weight, according to MedlinPlus. While humans can survive as long as a month without food, they can live only for four to 10 days without water. About 75 percent of muscle tissue and 20 percent of fat tissue is water. General recommendation for water intake range from six to eight glasses a day, but can vary based on activity, fitness level and other factors.
Balance
Water is needed to replace fluid lost through urine, perspiration and feces. The body regulates water balance through the sensation of thirst. When you have a low balance, your mouth becomes dry and sticky and you have an urge to drink something. Appropriate water intake is 2.7 liters to 3.7 liters a day for women and men, respectively, according to the National Strength and Conditioning Association. However, sweat and high activity can increase the required water intake.
Dehydration
Dehydration can range from mild discomfort such as headaches and cramps to more severe symptoms such as heatstroke and even death. A negative fluid balance of 3 percent to 5 percent of body weight can result in adverse cardiovascular effects, the National Strength and Conditioning Association reports. A 7 percent loss of fluid can result in fainting. Furthermore, people often undergo a phenomenon referred to as voluntary dehydration, in which they replace only about two-thirds of the water they lose throughout the day.
Assessing Fluid Loss
One commonly accepted way to assess your fluid loss is to consistently weigh yourself throughout the day, especially before and after exercise. Every pound lost during physical activity indicates one pint of fluid loss, the National Strength and Conditioning Association explains. Other signs of dehydration can include dark, strong-smelling urine, reduced urination, increased heart rate and muscle soreness.
Electrolytes
Electrolytes are minerals in the bloodstream that provide an electrical charge and help regulate several metabolic functions, according to MedlinePlus. Dehydration results in a loss of electrolytes, specifically the minerals sodium chloride and potassium. A loss in electrolytes can reduce muscle function and can cause a disruption in the bloodstream. Sports drinks often have additional electrolytes and can be more effective than just water for restoring hydration.
Exercise
Exercise creates perspiration and great fluctuations in hydration status. You should consume at least 16 oz. of fluid two hours before performing an exercise session to achieve appropriate hydration, the National Strength and Conditioning Association recommends. Furthermore, 6 to 8 oz. are advisable every 15 minutes while exercising. Finally, you should consume 16 oz. of fluid for every pound lost following exercise.
References
- MedlinePlus: Water in Diet
- "Essentials of Strength Training and Conditioning"; Thomas R. Baechle and Roger W. Earle (eds.); 2008
- MedlinePlus: Fluid and Electrolyte Balance
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