1. Thermoregulation: When we do high-intensity exercise, the body needs to regulate the body temperature to keep it constant. In order to lower the body temperature, the nervous system sends a signal to sweat glands to make them secrete sweat. When sweat evaporates, it will take away the heat on the body surface, thus lowering the body temperature.

2. Eliminate waste: Sweat contains waste components, such as water, salt and urea. Sweating can help the body get rid of these wastes and keep the balance of the environment in the body.

3. Keep the balance of water and salt: In the process of sweating, with the discharge of sweat, the body will also lose a certain amount of water and electrolyte. By supplementing water and electrolyte, the balance of water and salt in the body can be maintained.

4. Reduce muscle fatigue: During exercise, muscles produce a lot of lactic acid, which leads to muscle fatigue. Sweating can reduce the accumulation of lactic acid and relieve muscle fatigue by lowering muscle temperature.

5. Improve sports performance: Proper sweating can improve sports performance, because sweating helps to dissipate heat, reduce muscle fatigue and improve sports efficiency.

In a word, body sweating caused by fitness is a natural physiological reaction of the body, which helps to maintain body temperature balance, eliminate waste, maintain water and salt balance and improve sports performance. During exercise, it is very important to replenish water and electrolyte properly.