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Changes in upper limb muscle activity during smartphone usage while in stable and unstable positions and during gait
Phys Ther Rehabil Sci 2018;7:119-26
Published online September 30, 2018
© 2018 Korean Academy of Physical Therapy Rehabilitation Science.

You Lim Kima,c, Suk Min Leeb, Hyun-Soo Leec, Juyeong Songc, Si-On Songc, Min-Ji Seolc, Yu-Mi Jangc, Jin-Sik Imc, Ji-Woo Imc

aDivision of Healthcare Technology Assessment Research/National Evidence-based Healthcare Collaborating Agency, Seoul, Republic of Korea
bDepartment of Physical Therapy, College of Health and Welfare, Sahmyook University, Seoul, Republic of Korea
cDepartment of Physical Therapy, The Graduate School, Sahmyook University, Seoul, Republic of Korea
Correspondence to: Suk Min Lee (ORCID
Department of Physical Therapy, College of Health and Welfare, Sahmyook University, 815 Hwarang-ro, Nowon-gu, Seoul 01795, Republic of Korea
Tel: 82-2-3399-1632 Fax: 82-2-3399-1639 E-mail:
Received August 23, 2018; Revised September 14, 2018; Accepted September 14, 2018.
cc 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.
Objective: The objective of this study was to describe the influence of smartphone usage on the upper limb muscles while in stable and unstable positions and during gait.
Design: Cross-sectional study.
Methods: The study was conducted with 20 right-handed university students between 20 and 27 years of age. Experiments were carried out on students who have used cell phones for more than a year. In this study, experiments were performed with one-handed and two-handed smartphone operations while on stable ground, and the same parameters were measured during smartphone use on unstable ground and during gait. Subjects were instructed to write a text message in Korean on the smartphone for 3 minutes. This was repeated 3 times, with a rest period of 10 seconds given between each 3-minute period. Electromyography was used to record the muscle activity of the upper trapezius, extensor carpi radialis, extensor pollicis longus, and abductor pollicis (AP) during phone operation.
Results: The muscle activity value for the right AP in one-handed and the left-AP in two-handed operations was statistically higher than the other muscles in the stable position and during gait (p<0.0001). Also, the right AP in the one- handed operation condition was statistically higher than the two-handed condition (p<0.0001).
Conclusions: The use of smartphones while in a stable position resulted in high muscle activity of the right upper limb AP. However, in an unstable position, there were no significant differences from the other muscle activities. Using smartphone while assuming various positions may lead to musculoskeletal disorders in different places.
Keywords : Electromyography, Posture, Smartphone


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