The principle of body-building and muscle-building is to let the body ingest more nutrients such as protein, carbohydrate and fat through reasonable diet and exercise, and then during the rest period, the body will convert these extra nutrients into muscle tissue.

Specifically, fitness and muscle exercise need to follow the following principles:

1. Reasonable diet: ensure adequate intake of protein, carbohydrates, fat and other nutrients every day to support muscle growth and repair. In addition, it is necessary to control the intake of total calories to avoid fat accumulation caused by excessive intake.

2. High-intensity training: Stimulate the growth and repair of muscle tissue through weight-bearing training, and increase the number and size of muscle fibers. At the same time, proper aerobic exercise also helps to improve metabolic rate and promote fat burning.

3. Adequate rest: After exercise, give your body enough rest time to recover and re-establish muscle tissue. In addition, adequate sleep is also important for muscle gain.

4. Adhere to the long-term plan: muscle gain is a long-term process, which requires persistent exercise and diet management to achieve the desired results.