The design of the force-displacement characteristics or 'feel' of keyb
oard keyswitches has been guided by preference and performance data; t
here has been very little information on how switch 'feel' alters musc
le activity or applied force. This is a laboratory-based repeated meas
ures design experiment to evaluate the effect of computer keyboard key
switch design on applied finger force and muscle activity during a typ
ing task. Ten experienced typists typed on three keyboards which diffe
red in keyswitch make force (0.34, 0.47 and 1.02 N) while applied fing
ertip force and finger flexor electromyograms were recorded. The keybo
ard testing order was randomized and subjects typed on each keyboard f
or three trials, while data was collected for a minimum of 80 keystrok
es per trial. No differences in applied fingertip force or finger flex
or EMG were observed during typing on keyboards with switch make force
of 0.34 or 0.47 N. However, applied fingertip force increased by appr
oximately 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 1.0
2 N. These results suggest that, in order to minimize the biomechanica
l 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.