Woods Mitchell, Babski-Reeves Kari
Grado Department of Industrial and Systems Engineering, Virginia Tech, 250 Durham Hall, 0118, Blacksburg, 24061, USA.
Ergonomics. 2005 Dec 15;48(15):1793-808. doi: 10.1080/00140130500292087.
Several changes to computer peripherals have been developed to reduce exposure to identified risk factors for musculoskeletal injury, notably in keyboard designs. Negative keyboard angles and their resulting effects on objective physiological measures, subjective measures and performance have been studied, although few angles have been investigated despite the benefits associated with their use. The objective of this study was to quantify the effects of negative keyboard angles on forearm muscle activity, wrist posture, key strike force, perceived discomfort and performance and to identify a negative keyboard angle or range of keyboard angles that minimizes exposure to risk factors for hand/wrist injuries. Ten experienced typists (four males and six females) participated in a laboratory study to compare keyboard angles ranging from 0 degrees to -30 degrees , at 10 degrees increments, and a keyboard with a 7 degrees slope, using a wedge designed for use with standard QWERTY keyboards. Repeatability of exposures was examined by requiring participants to complete two test sessions 1 week apart. Dependent variable data were collected during 10 min basic data entry tasks. Wrist posture data favoured negative keyboard angles of 0 degrees (horizontal) or greater, compared to a positive keyboard angle of 7 degrees , especially for the flexion/extension direction. In general, the percentage of wrist movements within a neutral zone and the percentages of wrist movements within +/-5 degrees and +/-10 degrees increased as keyboard angle became more negative. Electromyography results were mixed, with some variables supporting negative keyboard angles whilst other results favoured the standard keyboard configuration. Net typing speed supported the -10 degrees keyboard angle, whilst other negative typing angles were comparable, if not better than, with the standard keyboard. Therefore, angles ranging from 0 degrees to -30 degrees in general provide significant reductions in exposure to deviated wrist postures and muscle activity and comparable performance.
为了减少对已确定的肌肉骨骼损伤风险因素的暴露，特别是在键盘设计方面，人们对计算机外围设备进行了多项改进。尽管负角度键盘设计有诸多益处，但针对其角度的研究较少，不过人们已经对负角度键盘及其对客观生理指标、主观指标和操作表现的影响进行了研究。本研究的目的是量化负角度键盘对前臂肌肉活动、手腕姿势、按键力度、感知不适和操作表现的影响，并确定一个能将手/腕部受伤风险因素暴露降至最低的负角度键盘或键盘角度范围。十名经验丰富的打字员（四名男性和六名女性）参与了一项实验室研究，使用专为标准QWERTY键盘设计的楔形物，比较从0度到-30度、以10度递增的键盘角度以及一个有7度坡度键盘的使用情况。通过要求参与者相隔1周完成两个测试环节来检验暴露的可重复性。在10分钟的基本数据输入任务期间收集因变量数据。与7度的正角度键盘相比，手腕姿势数据更倾向于0度（水平）或更大的负角度键盘，尤其是在屈伸方向上。一般来说，随着键盘角度变得更负，手腕在中立区内的运动百分比以及在+/- ±5度和+/-10度范围内的手腕运动百分比会增加。肌电图结果不一，一些变量支持负角度键盘，而其他结果则倾向于标准键盘配置。净打字速度支持-10度的键盘角度，而其他负角度打字时的速度即使不比标准键盘好，也与之相当。因此，一般来说，0度到-30度的角度能显著减少偏离手腕姿势和肌肉活动的暴露，且操作表现相当。
