1, isometric contraction: muscle contraction when its length remains the same and only the tension increases, this contraction is called isometric contraction. 2, isotonic contraction: muscle contraction is only the length of the shortening and tension remains unchanged, this contraction is called isotonic contraction. This is the muscle contraction when the load is less than the muscle contraction force generated by the situation, can make the object displacement. 3, centripetal contraction: muscle contraction, the muscle attachment area of the two ends of the tendon shortening close. 4, eccentric contraction: muscle contraction, the two ends of the muscle stop gradually extended farther, at this time the muscle contraction mainly lies in the control of its speed. 5, open chain movement (Open Kinetic Chain, OKC): refers to the movement of the proximal end of the limb fixed and distal joint activity. Such as walking when the swing phase. Open chain movement is characterized by a single joint to complete the movement. Such as dumbbell bending for biceps training, the elbow is fixed and the hand holds the dumbbell to do elbow flexion and extension movements. Injury rehabilitation functional exercise, because the shear force generated by the open chain movement is greater than the closed chain movement, should not choose the open chain movement to restore function, so as not to add to the burden of the injured part. In the later stages of rehabilitation, when the functionality and proprioception of the joint has been strengthened to a certain extent by closed chain exercises, open chain exercises can be used to target the muscle groups near the joint for sexual training. 6.Closed Kinetic Chain (CKC): refers to the movement of the distal end of the limb (palm or foot) that is fixed while the proximal end is active, such as the support phase when walking. Closed chain movements are characterized by the need for multiple joints to move in concert. For example, when using a barbell for weighted squat training, the foot is fixed and the hip, knee and ankle joints work in concert to complete the movement. Injury rehabilitation functional exercise, closed chain movement is a multi-joint synergistic movement that does not increase joint shear force, which can stimulate joint proprioceptors, produce limb movement and protective reflex arc (Protective Reflex Arc) activities, which can fully train the overall coordination of the joint and promote the recovery of joint proprioceptor function, thus promoting joint stability and functional rehabilitation, so early rehabilitation should Therefore, closed-chain exercises should be selected to restore function in the early stage of rehabilitation.