Differences in Muscle Activities of the Infraspinatus and Posterior Deltoid
during Shoulder External Rotation in Open Kinetic Chain and Closed Kinetic Chain
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| Authors: | Min-Hyeok Kang Jae-Seop Oh Jun-Hyeok Jang |
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| Affiliation: | 1) Department of Rehabilitation Science, Graduate School, Inje University, Republic of Korea;2) Department of Physical Therapy, College of Biomedical Science and Engineering, Inje University, Republic of Korea;3) Department of Physical Therapy, Haeundae Jaseng Hospital of Oriental Medicine, Republic of Korea |
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| Abstract: | [Purpose] This study investigated the changes in electromyographic (EMG) activities ofthe infraspinatus and posterior deltoid muscles during shoulder external rotation underopen kinetic chain (OKC) and closed kinetic chain (CKC) exercise conditions. [Subjects] Intotal, 15 healthy males participated in this study. [Methods] Subjects performed shoulderexternal rotations under CKC and OKC conditions while standing with and without weightsupport provided by a height-adjustable table. Pressure biofeedback was used to ensure aconstant amount of weight support. The activities of the infraspinatus and posteriordeltoid muscles during shoulder external rotation were measured using a wireless surfaceEMG system. The paired t-test was used to compare the EMG activities of the infraspinatusand the posterior deltoid muscles and the ratio of the infraspinatus to the posteriordeltoid during shoulder external rotation under OKC and CKC conditions. [Results] The EMGactivity of the infraspinatus and the ratio of the infraspinatus to the posterior deltoidactivities were significantly increased, whereas the posterior deltoid activity wassignificantly decreased under the CKC condition compared to the OKC condition.[Conclusion] Clinicians should consider the CKC shoulder external rotation exercise whenthey wish to selectively strengthen the infraspinatus.Key words: Infraspinatus, Posterior deltoid, Selective muscle strengthening |
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