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The Effect of Visual Feedback of Head Angles With Using a Mobile Posture-Aware System on Craniocervical Angle and Neck and Shoulder Muscles Fatigue During Watching the Smartphone
J Kor Phys Ther 2018;30(2):47-53
Published online April 30, 2018;
© 2018 The Korea Society of Physical Therapy.

Su Jeong Kim1, So Yeon Jeong2, Tae Lim Yoon3

1Department of Physical Therapy, Ppuri Medical Center, Cheongju; 2Department of Physical Therapy, National Transportation Rehabilitation Hospital, Yangpyeong; 3Department of Physical Therapy, College of Health and Medical Science, Cheongju University, Cheongju, Korea
Tae Lim Yoon
Received March 6, 2018; Revised April 17, 2018; Accepted April 26, 2018.
This is an Open Access article distribute 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: To find the effect of visual feedback of head angle with using a mobile posture-aware system on craniocervical angle and neck and shoulder muscles fatigue for preventing or decreasing the forward head posture.
Methods: Twenty-four healthy young adults in Chungbuk to participate in this study. The subjects started to watch a movie clip for 10 minutes with visual feedback in 0°, 30°, and 60° of head angles. During the task, surface electromyography (EMG) was used to collect data from the upper trapezius (UT), sternocleidomasetoid muscle (SCM), cervical erecter spinae (CES) during watching the smartphone. Craniocervical angles were measured using a sagittal-view photograph of the subject in a sitting posture. A one-way repeated analysis of variance with a significant level of 0.05 used for statistical analysis.
Results: Craniocervical angle with 0° visual feedback was significantly greater than 30°and 60°. Craniocervical angle with 30° visual feedback was significantly greater than 60°. In addition, MDF of UT muscles in 0° and 30° of visual feedback was significantly greater than 60°.
Conclusion: We concluded that 0° visual feedback of head angle with using a mobile posture-aware system would be beneficial to prevent or decrease forward head posture during watching a smartphone. We also could recommend using of 30° visual feedback in case of caring UT muscle fatigue primarily.
Keywords : Electromyography, Forward head posture, Head up application, Muscle fatigue

April 2018, 30 (2)
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