BACKGROUND AND AIM: Daily use of personal computer (PC) is extraordinary increasing. Long PC work is apt to bring round-shouldered posture, induce eyestrain, and neck shoulder region (NSR) ache, resulting in the onset of "Repetitive Stress Injury (RSI)". We have previously developed and reported tactile information to the body from special under wear is effective to improve standing and walking posture. Aim of the current study is to examine the effect of new inner wear specially designed for PC work (PC-inner, special patch on the back) based on the hypothesis to help the function of tholacolumber fascia and to decrease COG change of upper body. We expected the state-of-the art designed PC-inner balance the NSR muscle activities and avoid NSRA and RSI.
METHODS: Kinematic, kinetic and electromyography analyses were performed to determine effects of posture-support underwear (PC-inner) compare to control underwear (AIRism, UNIQLO CO., LTD) at quiet rest and during PC-work and quiet standing by using 3D motion analysis system (VICON-MX, Oxford Matrics Inc.) , force plate (OR6-WP, AMTI Inc.) and surface electromyography (Noraxon Inc.). Quiet sitting posture with wearing PC-wear or control wear was evaluated using Vicon. For standing posture, quantity of spatial displacement was calculated at the middle point of four markers stick on the head and pelvis region. Subjects are 10 healthy adults students ages between 20-25 years old.
RESULTS: PC-inner significantly brought quiet sitting posture to decrease trunk flexion angle (more extended position of trunk). PC-inner wearing influenced the gradual decrease of laterality difference of EMG of muscles of scalene, sternocleidomastoid, splenius cervicis during 5 min typing. Interestingly, EMG trapezius with control wear linearly increased during 5 min, while laterality ratio of trapezius EMG wearing PC-inner conversely decreased and attained to 1.0 (no difference of left and right). Spatial displacement at standing posture was also diminished compare to control under wear.