Dehydration after exercise, usually called exercise dehydration, refers to the excessive loss of fluids and electrolytes in the body after exercise. Athletes will sweat a lot when they exercise in high temperature and high humidity. If he doesn't replenish water in time, he is prone to exercise dehydration. Therefore, for us ordinary bodybuilders, we should try to avoid strenuous exercise in hot summer, choose to exercise in the morning or evening, and pay attention to rehydration before, during and after exercise. In addition, athletes who need to control their weight before the competition (such as Sanda, weightlifting, etc.) will lose a lot of water by sauna, plastic wrap, etc., and are also prone to exercise dehydration. Exercise dehydration is usually accompanied by the loss of electrolytes (such as sodium ions) at the same time. According to the degree of body fluid loss, it can be divided into mild (water loss accounts for 2%~3% of body weight), moderate (water loss accounts for 3%~6% of body weight) and severe (water loss accounts for more than 6% of body weight).