Effects of the height of ball-backrest on head and shoulder posture and trunk muscle activity in VDT workers.
This study was designed to elucidate the effects of a ball-backrest at different heights on the head and shoulder posture and neck and trunk muscles of visual display terminal (VDT) workers who adopted a forward head posture when working at a VDT. Twenty-three VDT workers with forward head posture performed the keyboard typing work at a VDT without and with a ball-backrest at the L3, T10, and T4 levels. Surface electromyograms were recorded from the neck, shoulder, and trunk muscles, and the forward head angle and forward shoulder angle were analyzed using a 3-D motion analysis system. The significance of differences for the ball-backrest at different heights was tested by repeated one-way ANOVA, with the significance cutoff set at p=0.05. The mean forward head angle and forward shoulder angle decreased in the order of no backrest, T10-level ball-backrest, T4-level ball-backrest. Compared with not using a backrest, the activity of midcervical muscles was significantly lower and that of the lower trapezius was significantly higher when using a T4-level ball-backrest, and the activity of the internal oblique abdominal muscle was significantly higher when using a T10-level ball-backrest. We suggested that using T4 and T10-level ball-backrests would produce similar effects to active exercise, such as ball exercise for trunk stabilization, and that a ball-backrest would prevent kinematics changes. Therefore, the height of the backrest must be determined on the basis of the characteristics of work-related musculoskeletal disorders when applying a ball-backrest to VDT workers with such disorders.
Yoo
Won-gyu
WG
Department of Physical Therapy, College of Biomedical Science and Engineering, Inje University, 607 Obangdong, Gimhae, Gyeongsangnam-do, 621-749 Republic of Korea.
Yi
Chung-hwi
CH
Cho
Sang-hyun
SH
Jeon
Hye-seon
HS
Cynn
Heon-seock
HS
Choi
Houng-sik
HS
D000328:Adult; D016288:Computer Terminals; D012090:Cumulative Trauma Disorders / Q000209:etiology / Q000517:prevention & control*; D004867:Equipment Design; D006804:Ergonomics / Q000379:methods*; D005260:Female; D019416:Head Movements / Q000502:physiology; D006801:Humans; D007374:Interior Design and Furnishings; D008297:Male; D009140:Musculoskeletal Diseases / Q000209:etiology / Q000517:prevention & control*; D009333:Neck / Q000502:physiology; D009784:Occupational Diseases / Q000209:etiology / Q000517:prevention & control; D011187:Posture / Q000502:physiology*; D012782:Shoulder / Q000502:physiology; D014584:User-Computer Interface