Yoo Won-gyu, Yi Chung-hwi, Cho Sang-hyun, Jeon Hye-seon, Cynn Heon-seock, Choi Houng-sik
Department of Physical Therapy, College of Biomedical Science and Engineering, Inje University, 607 Obangdong, Gimhae, Gyeongsangnam-do, 621-749 Republic of Korea.
Ind Health. 2008 Jul;46(3):289-97. doi: 10.2486/indhealth.46.289.
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.
本研究旨在阐明不同高度的球型靠背对视觉显示终端（VDT）工作者头部和肩部姿势以及颈部和躯干肌肉的影响，这些工作者在使用VDT工作时头部呈前伸姿势。23名头部呈前伸姿势的VDT工作者在无球型靠背以及有L3、T10和T4水平球型靠背的情况下在VDT上进行键盘打字工作。记录颈部、肩部和躯干肌肉的表面肌电图，并使用三维运动分析系统分析头部前伸角度和肩部前伸角度。通过重复单因素方差分析检验不同高度球型靠背差异的显著性，显著性临界值设定为p = 0.05。头部前伸平均角度和肩部前伸平均角度按照无靠背、T10水平球型靠背、T4水平球型靠背的顺序降低。与不使用靠背相比，使用T4水平球型靠背时颈中肌的活动显著降低，下斜方肌的活动显著升高，使用T10水平球型靠背时腹内斜肌的活动显著升高。我们认为，使用T4和T10水平的球型靠背会产生与主动运动类似的效果，如用于躯干稳定的球运动，并且球型靠背可以防止运动学变化。因此，在将球型靠背应用于患有此类疾病的VDT工作者时，必须根据与工作相关的肌肉骨骼疾病的特征来确定靠背的高度。
