Biomedical subjects

E Serina

Publications and source records attributed to E Serina.

2 recordsLinked to original sources

PubMed1997

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

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.

Adult↗

PubMed1996

Keyboard reaction force and finger flexor electromyograms during computer keyboard work.

This study examines the relationship between forearm EMGs and keyboard reaction forces in 10 people during keyboard tasks performed at a comfortable speed. A linear fit of EMG force data for each person and finger was calculated during static fingertip loading. An average r2 of .71 was observed for forces below 50% of the maximal voluntary contraction (MVC). These regressions were used to characterize EMG data in force units during the typing task. Averaged peak reaction forces measured during typing ranged from 3.33 N (thumb) to 1.84 N (little finger), with an overall average of 2.54 N, which represents about 10% MVC and 5.4 times the key switch make force (0.47 N). Individual peak or mean finger forces obtained from EMG were greater (1.2 to 3.2 times) than force measurements; hence the range of r2 for EMG force was .10 to .46. A closer correspondence between EMG and peak force was obtained using EMG averaged across all fingers. For 5 of the participants the force computed from EMG was within +/-20% of the reaction force. For the other 5 participants forces were overestimated. For 9 participants the difference between EMG estimated force and the reaction force was less than 13% MVC. It is suggested that the difference between EMG and finger force partly results from the amount of muscle load not captured by the measured applied force.

Adult↗