Introduction:Single force-displacement characteristics of mechanical key switches have been shown to affect performance, fatigue and discomfort during keyboard use. This study compared the effects of mechanical key switches with differing force-displacement characteristics on forearm muscle activity, typing performance, Fitts Study task performance, subjective fatigue and user preference. Methods: Using a within subjects intervention study of crossover design, 64 subjects completed modified Fitts and typing tasks on five different mechanical key switches to mimic dual word processing and gaming keyboard use. Bilateral muscle activity was recorded using surface electromyography (EMG); typing and Fitts task performance measures were tracked. Results: The key switch with a linear force displacement curve had higher net strokes and lower net typing speed than two key switches with tactile feedback (p<0.05). The key switch with the longest tactile travel, operating travel and highest bottom force required slightly higher peak muscle activity compared to 2 other key switches with lower values (p<0.05). Key switches with shorter tactile and operating travel and lower bottom forces were preferred over other key switches.Conclusions: Among mechanical key switches, a linear force displacement curve had the worst outcomes; key switches with shorter tactile (1.2mm) and operating travel (2.0mm) and a lower bottom force (35-40g) had best outcomes overall.
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