Muscle spindle is a kind of pain receptor to control muscles from being overstretched, and tendon spindle is a kind of tension receptor. Muscle spindle and tendon spindle, as reflex receptors of the body, play an important role in maintaining human posture and coordinating movement. Therefore, the more muscle fibers are destroyed by excessive centrifugal contraction during centrifugal exercise, the more helpful it will be for your excessive muscle recovery in the future. Because after the muscle gap is enlarged, protein will be absorbed more easily, thus greatly increasing your muscle mass. It happens when the contraction force and resistance are equal and the muscle length does not change significantly. Isometric contraction is easy to observe in resistance training, such as the pause between lifting and descending stages. The type of muscle contraction determines the form of exercise, and the contraction of skeletal muscle depends on the needs of muscle work. According to the changes of skeletal muscle contraction, it can be divided into the following four forms: centripetal contraction, centrifugal contraction, isometric contraction and isokinetic contraction.

Centrifugation needs a series of good control and strength. It is difficult for junior fitness enthusiasts to do centrifugation well because of insufficient foundation, so everyone pays more attention to centripetal force. However, at high levels, people often deliberately do centrifugation to make muscles stronger after repair. Centripetal contraction trains muscle reaction and explosive force, while centrifugal contraction really enhances muscle's ability to bear weight, including muscle strength and muscle endurance. Muscles are gradually elongated under resistance, which makes the movement link move in the opposite direction of muscle tension. It is a kind of dynamic contraction, also called concession contraction, and its maximum muscle strength is greater than centripetal contraction.

Isometric contraction refers to muscle contraction in which the length remains the same and the tension changes. In this contracted state, muscle tension can be maximized. However, because there is no displacement, physically speaking, muscles do not do external work, but they still need to consume a lot of energy. A large part of people's quality is born, and it is also the result of acquired environment and training. You can't judge others' progress or retrogression just because of their strengths. This is not the correct training attitude.