The effect of keyboard keyswitch make force on applied force and finger flexor muscle activity

Abstract

The design of the force-displacement characteristics or 'feel' of keyboard keyswitches has been guided by preference and performance data; there has been very little information on how switch 'feel' alters muscle activity or applied force. This is a laboratory-based repeated measures design experiment to evaluate the effect of computer keyboard keyswitch design on applied finger force and muscle activity during a typing task. Ten experienced typists typed on three keyboards which differed in keyswitch make force (0.34, 0.47 and 1.02 N) while applied fingertip force and finger flexor electromyograms were recorded. The keyboard testing order was randomized and subjects typed on each keyboard for three trials, while data was collected for a minimum of 80 keystrokes per trial. No differences in applied fingertip force or finger flexor EMG were observed during typing on keyboards with switch make force of 0.34 or 0.47 N. However, applied fingertip force increased by approximately 40% (p < 0.05) and EMG activity increased by approximately 20% (p < 0.05) when the keyswitch make force was increased from 0.47 to 1.02 N. These results suggest that, in order to minimize the biomechanical loads to forearm tendons and muscles of keyboard users, keyswitches with a make force of 0.47 N or less should be considered over switches with a make force of 1.02 N.

Impact Activation Improves Rapid Button Pressing

“…Button design is known to affect users' peak force, tapping rate, comfort level, and muscle activity [17,19]. The defining parameters of a button's response are travel depth, spring stiffness, and position of activation point.…”

An inexpensive and accurate method of measuring the force of responses in reaction time research

“…there is ample evidence to suggest (Gerard, Armstrong, Rempel, & Woolley, 2002;Rempel et al, 1997) that the design of modern computer keys serves to constrain, but not control, the force used to respond to stimuli.…”

Effects of a Multitouch Keyboard on Wrist Posture, Typing Performance and Comfort

“…Past research has shown that there was no significant difference in finger force or EMG activity when typists used a keyboard with a make force of 0.43N and a keyboard with a make force of 0.47N (Rempel et al, 1997). When a keyboard of 1.02N make force was introduced, fingertip force and EMG activity increased significantly (p<0.05) by 40% and 20% respectively.…”

“…Finger force data, used in Rempel et al (1997) should be collected to show the actual key strike force applied to the keyboard by the subjects. This would be especially helpful in determining whether a no-force keyboard causes users to decrease key strike force.…”