Electromyographic Comparisons between Open and Closed Kinetic Chain Knee Exercises

Abstract

Traditionally, the open kinetic chain (OKC) exercises, prescribed in the knee rehabilitation program, may produce undue shear force at certain specific knee flexion angles. This undue shear force may jeopardize the reconstructed anterior cruciate ligament. Therefore, many complicatiois after ACL reconstruction surgery may occur such as joint stiffness, loss joint range of motion, and patellofemoral pain. The clinical use of closed kinetic chain (CKC) exercises has significantly increased for the past years. Many investigators believed that CKC exercises produced less anterioposterior shear force and thus reduced stress on the reconstructed ACL. Indeed, the joint mechanics and muscle recruitment during CKC exercises may be different from OKC exercises. Among several CKC exercises, isokinetic leg press exercise has been still lacking of motor control investigation support. Especially, therapeutic justification and clinical elucidation are needed in knee rehabilitation programs. Therefore, the purpose of this study was to compare the differences of electromyographic activities among commonly used rehabilitation movements: OKC knee extension, OKC knee flexion and the CKC leg press exercises. The results, in the present study, showned that OKC knee extension may cause knee extensor maximally activated (1.35 ± 1.15 MVC) but cause knee flexor minimally activated. In contrast, OKC knee flexion may cause knee flexor maximally activated (1.11 ± 0.11 MVC) but cause knee extensor minimally activated. The CKC leg press showed balance in muscle recruitment between knee extensor (0.52 ± 0.32 MVC) and flexor (0.62 ± 0.17 MVC). Since CKC leg press exercise caused both knee extensor and flexor co-activated at a given same knee flexion angle when compared with OKC knee extension and flexion movement. In the early phase of ACL reconstruction, CKC leg press exercise may consider as a safer exercise. Through, knee extensor and flexor co-activated, CKC leg press may provide a higher stabilization effect than OKC knee extension and flexion exercises. Additionally, the CKC leg press exercise can be used to strengthen knee extensor and flexor, simultaneously.