Proper hydration is essential for normal body function, physical activity, and athletic performance. The goal of hydration is to prevent dehydration without over-drinking, which varies by individual. Hydration status can be monitored through urine color (light indicates good hydration) and changes in body weight before and after exercise to estimate sweat loss.
Dehydration can occur in any environment or activity, even in cold weather or while swimming, and performance declines when fluid loss exceeds 2% of body weight. Factors that increase fluid loss include high temperatures, exercise intensity and duration, body size, gender, and fitness level. Well-trained athletes often sweat more and therefore need more fluids.
Common signs of dehydration include intense thirst, fatigue, increased body temperature, rapid breathing and heart rate, confusion, and fainting. To maintain hydration, athletes should drink fluids before, during, and after exercise. Water is generally sufficient, but sports drinks are recommended for moderate- to high-intensity exercise lasting longer than an hour to help replace fluids lost through sweat.