The human body has about 639 muscles throughout the body, and the weight of these muscles accounts for about 35% to 45% of the body weight. According to the structure and function of the human body muscle can be divided into: smooth muscle, skeletal muscle and cardiac muscle. According to the different forms can be divided into: long muscles, short muscles, broad muscles and rotator cuff muscles. Human muscle contains a lot of water, the most important part of the muscle is muscle fiber, the human body is composed of about 6 billion muscle fibers, the longest can be up to 60 centimeters, the shortest is only about 1 mm.