开链运动与闭链运动

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In open kinetic chain (OKC) exercise, the terminal segment of the extremity moves freely without any external resistance. The sequential activation of muscles in OKC exercise from proximal to distal allows rapid acceleration and speed of the distal segment. In closed kinetic chain (CKC) exercise, the distal segment of the extremity is fixed, and proximal motion takes place in multiple planes.

A common error in developing an exercise program is failure to assess the proximal and distal segments of the entire extremity, or kinetic chain. A kinematic chain is a series of interrelated joints that constitute a complex motor unit, constructed so that motion at one joint will produce motion at the other joints in a predictable manner. Whereas kinematics describes the appearance of motion, kinetics involves the forces, whether internal (e.g., muscle contractions or connective tissue restraints) or external (e.g., gravity, inertia, or segmental masses) that affect motion. Initially, a closed kinetic chain (CKC) was characterized as the distal segment of the extremity in an erect, weight-bearing position, such as the lower extremity when a person is weight bearing. Subsequently, when the distal segment of the extremity is free to move without causing motion at another joint, such as when non-weight bearing, the system was referred to as an open kinetic chain (OKC). When force is applied, the distal segment may function independently or in unison with the other joints. Movements of the more proximal joints are affected by OKC and CKC positions. For example, the rotational components of the ankle, knee, and hip reverse direction when moving from an OKC to CKC position.

Because of incongruities between the lower and upper extremity, particularly in the shoulder region, several authors have challenged the traditional definition of OKC and CKC positions. Stabilizing muscles in the scapulothoracic region produces a joint compression force that stabilizes the glenohumeral joint much in the same manner as a CKC in the lower extremity. Although debate continues on defining CKC and OKC relative to the upper extremity, there remains general agreement that both CKC and OKC exercises should be incorporated into an upper and lower extremity rehabilitation program.

Injury and subsequent immobilization can affect the proprioceptors in the skeletal muscles, tendons, and joints. In rehabilitation, it is critical that CKC activities be used to retrain joints and muscle proprioceptors to respond to sensory input. Closed kinetic chain exercises are recommended for several reasons. Closed kinetic chain exercises stimulate the proprioceptors, increase joint stability, increase muscle coactivation, allow better utilization of the SAID (Specific Adaptations to Imposed Demands) principle, and permit more functional patterns of movement and greater specificity for athletic activities.

In contrast, OKC exercises can isolate a specific muscle group for intense strength and endurance exercises. In addition, they can develop strength in very weak muscles that may not function properly in a CKC system because of muscle substitution. Although OKC exercises may produce great gains in peak force production, the exercises are usually limited to one joint in a single plane (uniplanar), have greater potential for joint shear, have limited functional application, and have limited eccentric and proprioceptive retraining. However, OKC exercises can assist in developing a patient-athletic trainer rapport through uniplanar and multiplanar manual therapeutic techniques.

When ROM has been achieved, repetition of motion through actual skill movements can improve coordination and joint mechanics as the individual progresses into phase three of the program. For example, a pitcher may begin throwing without resistance or force application in front of a mirror to visualize the action. This also can motivate the individual to continue to progress in the therapeutic exercise program.

1. Wagman D, Khelifa M. Psychological issues in sport injury rehabilitation:current knowledge and practice. J Ath Train 1996;31(3):257-261.
2. Scherzer CB, et al. Psychological skills and adherence to rehabilitation after reconstruction of the anterior cruciate ligament. J Sport Rehab 2001;10(3):165-172.
3. Wilk KE, Arrigo CA, Andrews JR. Closed and open kinetic chain exercise for the upper extremity. J Sports Rehab 1996;5(1):88-102.
4. Dillman CH, Murray TA, Hintermeister RA. Biomechanical differences of open and closed chain exercises with respect to the shoulder. J Sports Rehab 1994;3(3):228-23.

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