Differences in Muscle Activities of the Infraspinatus and Posterior Deltoid during Shoulder External Rotation in Open Kinetic Chain and Closed Kinetic Chain Exercises

Abstract

[Purpose] This study investigated the changes in electromyographic (EMG) activities of the infraspinatus and posterior deltoid muscles during shoulder external rotation under open kinetic chain (OKC) and closed kinetic chain (CKC) exercise conditions. [Subjects] In total, 15 healthy males participated in this study. [Methods] Subjects performed shoulder external rotations under CKC and OKC conditions while standing with and without weight support provided by a height-adjustable table. Pressure biofeedback was used to ensure a constant amount of weight support. The activities of the infraspinatus and posterior deltoid muscles during shoulder external rotation were measured using a wireless surface EMG system. The paired t-test was used to compare the EMG activities of the infraspinatus and the posterior deltoid muscles and the ratio of the infraspinatus to the posterior deltoid during shoulder external rotation under OKC and CKC conditions. [Results] The EMG activity of the infraspinatus and the ratio of the infraspinatus to the posterior deltoid activities were significantly increased, whereas the posterior deltoid activity was significantly decreased under the CKC condition compared to the OKC condition. [Conclusion] Clinicians should consider the CKC shoulder external rotation exercise when they wish to selectively strengthen the infraspinatus.

The effect of exercise types for rotator cuff repair patients on activities of shoulder muscles and upper limb disability

“…Therefore, this study investigated the changes in the activities of shoulder muscle, fatigue, and upper limb disability of rotator cuff repair patients after open kinetic chain exercise or closed kinetic chain exercise performed at the end of the protection period. Jang19 ) studied the effects of open kinetic chain exercise and closed kinetic chain exercise at different shoulder angles on 15 normal persons. The infraspinatus muscle had higher muscle activity than the other muscles in the closed kinetic chain exercise at 45 degrees group.…”

“…The closed kinetic chain exercise group subjects performed the exercise in the same position, but with the distal part of the arm attached to a pressure biofeedback unit, to prevent compensation, with the intial pressure set to 20 mmHg. After setting the pressure, the subjects fixed the distal part of arm performed the exercise without exceeding 40 mmHg with all the fingers facing outward19 ) . The exercise was performed without inducing pain.…”

Changes in the electromyographic activities of the infraspinatus and posterior deltoid according to abduction angles of the shoulder joint during shoulder external rotation in closed kinetic chain exercise

“…This study referred to research by Kang et al3 ) and used a pressure bio-feedback unit during closed kinetic chain exercises because muscle activity was expected to differ during closed kinetic exercises performed at weight-bearing levels. In the present study, activity of the infraspinatus muscle showed no statistically significant differences (p>0.05).…”

“…Kang et al maintained that closed kinetic chain exercises are more effective than open kinetic chain exercises at activating the infraspinatus muscle while minimizing the activity of the posterior deltoid muscle3 ) . Jang and Oh claimed that when the shoulder is bent at 45 degrees, the activity of the posterior deltoid muscle is reduced4 ) .…”

“…Jung et al conducted research on the activity of the infraspinatus muscle during passive shoulder and active elbow exercises7 ) . While there have been studies on the effectiveness of exercises designed to strengthen the infraspinatus muscle, little research has been carried out on the shoulder abduction angles suitable for strengthening this muscle and minimizing the use of the posterior deltoid muscle8 ) . Therefore, the purpose of this study was to compare the activity of the infraspinatus and the posterior deltoid muscles at different abduction angles of the shoulder joint during closed kinetic chain exercises.…”