Kotani K, Barrero L H, Lee D L, Dennerlein J T
Department of Systems Management Engineering, Kansai University, Osaka, Japan.
Ergonomics. 2007 Sep;50(9):1419-32. doi: 10.1080/00140130701330587.
The distance of the keyboard from the edge of a work surface has been associated with hand and arm pain; however, the variation in postural and muscular effects with the horizontal position have not been explicitly explored in previous studies. It was hypothesized that the wrist approaches more of a neutral posture as the keyboard distance from the edge of table increases. In a laboratory setting, 20 adults completed computer tasks using four workstation configurations: with the keyboard at the edge of the work surface (NEAR), 8 cm from the edge and 15 cm from the edge, the latter condition also with a pad that raised the work surface proximal to the keyboard (FWP). Electrogoniometers and an electromagnetic motion analysis system measured wrist and upper arm postures and surface electromyography measured muscle activity of two forearm and two shoulder muscles. Wrist ulnar deviation decreased by 50% (4 degrees ) as the keyboard position moved away from the user. Without a pad, wrist extension increased by 20% (4 degrees ) as the keyboard moved away but when the pad was added, wrist extension did not differ from that in the NEAR configuration. Median values of wrist extensor muscle activity decreased by 4% maximum voluntary contraction for the farthest position with a pad (FWP). The upper arm followed suit: flexion increased while abduction and internal rotation decreased as the keyboard was positioned further away from the edge of the table. In order to achieve neutral postures of the upper extremity, the keyboard position in the horizontal plane has an important role and needs to be considered within the context of workstation designs and interventions.
键盘与工作表面边缘的距离与手部和手臂疼痛有关；然而，以往研究尚未明确探讨水平位置变化对姿势和肌肉的影响。研究假设，随着键盘与桌子边缘距离的增加，手腕更接近中立姿势。在实验室环境中，20名成年人使用四种工作站配置完成计算机任务：键盘位于工作表面边缘（近位）、距离边缘8厘米和距离边缘15厘米，后一种情况还在键盘近端放置了一个抬高工作表面的垫子（远位抬高）。电子角度计和电磁运动分析系统测量手腕和上臂姿势，表面肌电图测量两块前臂肌肉和两块肩部肌肉的肌肉活动。随着键盘位置远离使用者，手腕尺侧偏斜减少了50%（4度）。在没有垫子的情况下，随着键盘移开，手腕伸展增加了20%（4度），但添加垫子后，手腕伸展与近位配置时没有差异。在有垫子的最远位置（远位抬高），手腕伸肌肌肉活动的中位数减少了4%的最大自主收缩。上臂也有类似变化：随着键盘离桌子边缘更远，上臂屈曲增加，外展和内旋减少。为了实现上肢的中立姿势，键盘在水平面上的位置起着重要作用，需要在工作站设计和干预的背景下加以考虑。
