Title: Exploratory study on adequacy of upper extremity position during smartphone usage

Authors: Han-Yeong Yun; Tae-Lim Yoon

Addresses: Department of Physical Therapy, Cheongju Hana Hospital, Cheongju, South Korea ' Department of Physical Therapy, College of Health and Medical Science, Cheongju University, 298, Daeseong-ro, Cheongwon-gu, Cheongju-si, Chungcheongbuk-do, South Korea

Abstract: This study compared the effects of the prone, side-lying, and sitting positions during smartphone use. Positions can cause discomfort in the upper extremity musculoskeletal system. Thirty healthy young adults were recruited and instructed to type on a smartphone for 5 min in each position and 5 min rest between each position. Electromyography data acquired from the upper extremity muscles were analysed using the amplitude probability distribution function (APDF) method. Wrist and elbow joint angles were assessed using the motion analysis system (MyoMotion). In 50% of APDFs, the flexor carpi ulnaris muscle displayed higher muscle activity in the side-lying position, whereas the abductor pollicis brevis (APB) and extensor carpi ulnaris (ECU) muscles showed higher muscle activity in the sitting position. In 90% of APDF, the upper trapezius, ECU, and APB muscles showed higher muscle activity in the sitting position. Additionally, the side-lying position showed a neutral wrist extension angle of 0° compared to the prone and sitting positions (p < 0.05). Using smartphones in the side-lying position is recommended to reduce overuse of the upper-extremity muscles and poor alignment of the wrists.

Keywords: smartphone; typing; positions; sitting; prone; side-lying; surface electromyography; MyoMotion; amplitude probability distribution function; APDF.

DOI: 10.1504/IJHFE.2019.105362

International Journal of Human Factors and Ergonomics, 2019 Vol.6 No.4, pp.390 - 402

Received: 02 Apr 2019
Accepted: 21 Oct 2019

Published online: 17 Feb 2020 *

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