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Comparison of the Effects of Different Adduction Loads on EMG Activities of Selected Shoulder Muscles During Shoulder External Rotation Exercise in Healthy Young People
J Korean Soc Phys Med 2019;14(2):1-7
Published online May 31, 2019;
© 2019 Journal of The Korean Society of Physical Medicine.

Cheng Peng, PT, MS · Chang-Hwan Bae, PT, PhD1 · Eun-Hong Choi, PT, MS2 · Myoung-Kwon Kim, PT, PhD3†

Department of Rehabilitation Sciences, Graduate School, Daegu University,
1Bae Chang Hwan Training Center, Samsan-ro, Nam-gu, Ulsan, 37, Republic of Korea,
2Department of Rehabilitation Sciences, Graduate School, Daegu University,
3Department of Physical Therapy, College of Rehabilitation Sciences, Daegu University
Received November 3, 2018; Revised November 22, 2018; Accepted March 6, 2019.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
PURPOSE: This study was conducted to investigate effects of shoulder adduction load on rotator cuff muscles, including the infraspinatus, during the external rotation exercise of shoulder.
METHODS: This study investigated 16 healthy university students from Daegu University. Before the study started, all participants understood the content of this study. They signed an informed consent form. Five electrodes for surface electromyography (sEMG) were attached to their infraspinatus, middle deltoid, posterior deltoid, upper trapezius and pectoralis major. The participants then underwent the shoulder external rotation exercise with the shoulder adduction at three loads (0 mmHg, 20 mmHg and 40 mmHg) that were controlled using a stabilizer Pressure Biofeedback™ device. The surface electrodes recorded the electromyographic data during the external rotation exercise of shoulder.
RESULTS: The infraspinatus was most activated when the shoulder adduction pressure was 40 mmHg during the external rotation exercise of shoulder. The infraspinatus activation significantly increased when the shoulder adduction pressure intensity increased, while the middle deltoid activation and the posterior deltoid activation significantly decreased (p<.05).
CONCLUSION: In conclusion, increases in shoulder adduction load intensity during shoulder external rotation exercises can have a positive effect on the infraspinatus, which consists of rotator cuff muscles, with minimal activity in the middle and posterior deltoid.
Keywords : Adduction load, Electromyography, Rotator cuff, Shoulder

May 2019, 14 (2)
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