Radwin R G, Ruffalo B A
Department of Industrial Engineering, University of Wisconsin-Madison 53706, USA.
Ergonomics. 1999 Jan;42(1):160-70. doi: 10.1080/001401399185865.
This study investigates the effects of key switch design parameters on short-term localized muscle fatigue in the forearm and hand. An experimental apparatus was utilized for simulating and controlling key switch make force and travel using leaf spring mechanisms, and provided direct measurement of applied key strike force using strain gauge load cells. Repetitive key tapping was performed as fast as possible using the dominant index finger for 500 s per condition (8.3 min) and a work-rest schedule consisting of 15 s of key tapping alternating with 10 s of rest. One combination of two make force levels (0.31 and 0.71 N) and two over travel distances (0.5 and 4.5 mm) was presented randomly on four different days. Nine subjects participated. Localized muscle fatigue in the hand and forearm was assessed subjectively using a 10 cm visual analogue scale, and objectively using surface electromyography (EMG). Average peak key strike force exerted was 0.35 N less for the smaller make force and 0.59 N less for the longer over travel distance. Fatigue occurred in all cases but no significant differences were observed between key switch parameters based on RMS EMG. Subjective reports of localized fatigue after 500 s were less when the key switch make force was less; however, a corresponding over travel effect was not observed despite the greatly reduced key strike force for the longer over travel distance. This discrepancy may be explained by the greater finger movement that was observed with increased over travel. Although there was no apparent improvement in short-term discomfort from fatigue when over travel was increased, this study did not consider the potential long-term health benefits from reduced key strike force.
本研究调查了按键开关设计参数对前臂和手部短期局部肌肉疲劳的影响。使用实验装置，通过板簧机构模拟和控制按键开关的闭合力和行程，并使用应变片式称重传感器直接测量施加的按键敲击力。在每种条件下，使用优势食指尽可能快地进行500秒（8.3分钟）的重复按键敲击，工作-休息模式为15秒的按键敲击与10秒的休息交替进行。两种闭合力水平（0.31和0.71牛）和两种超出行程距离（0.5和4.5毫米）的一种组合在四个不同的日子随机呈现。九名受试者参与。使用10厘米视觉模拟量表主观评估手部和前臂的局部肌肉疲劳，并使用表面肌电图（EMG）进行客观评估。较小闭合力下施加的平均峰值按键敲击力小0.35牛，较长超出行程距离下小0.59牛。所有情况下均出现疲劳，但基于均方根肌电图，未观察到按键开关参数之间存在显著差异。当按键开关闭合力较小时，500秒后局部疲劳的主观报告较少；然而，尽管较长超出行程距离下按键敲击力大幅降低，但未观察到相应的超出行程效应。这种差异可能是由于随着超出行程增加观察到手指运动更大。尽管增加超出行程时短期疲劳不适没有明显改善，但本研究未考虑降低按键敲击力可能带来的长期健康益处。
