Wrist postures in video display terminal operators (VDT) using different keyboards

Abstract

This study examined the differences in wrist motion using three types of keyboards: a standard QWERTY design and two alternative designs, the Truform Ergonomic keyboard and the Health Care Comfort keyboard. The Comfort keyboard (adjusted at a lateral slope of 30° and horizontal split of 20° and the Truform keyboard (with a 20° horizontal split) were compared with the standard flat QWERTY keyboard. Twenty adult video display terminal (VDT) workers from the Boston area ranging from 22 to 68 years of age volunteered to participate in this study. In randomly assigned sequences, participants typed for 5 min on each keyboard while their wrist motions were measured using the WristSystem by Greenleaf Medical Systems, Inc. Contrast score analysis was used to analyze mean values in flexion-extension and radial-ulnar deviation of the right and left hands between the three sessions. The alternative keyboards significantly reduced ulnar deviation (left: t(19) = 3.46, P < 0.0025; right: t(19) = 5.83, P < 0.00001), and extension (left: t(19) = 2.82, P < 0.001; right: t(19) = 3.99, P < 0.0005). Results suggest that the Comfort keyboard yielded less ulnar deviation and extension as compared to the standard QWERTY keyboard (Left Extension: QWERTY mean = 21.45, Comfort mean = 18.67; Right Extension: QWERTY mean = 22.9, Comfort mean = 14.45; Left Ulnar Deviation: QWERTY mean = 14.54, Comfort mean = 7.44; Right Ulnar Deviation: QWERTY mean = 17.1, Comfort mean = 6.12). Although the Truform keyboard reduced ulnar deviation (Left: QWERTY mean = 14.54, Truform mean = 9.42; Right: QWERTY mean = 17.1, Truform mean = 9.67), it also yielded extension values comparable to those using the QWERTY (Left Extension: QWERTY mean = 21.45, Truform mean = 24.66; Right Extension: QWERTY mean = 22.9; Truform mean = 22.4). Both alternative designs yielded slightly higher values for radial deviation (left: t(19)=-2.4, P > 0.25; right: t(19)=-3.75, P > 0.25) and flexion (left: t(19)=-1.39, P > 0.25; right: t(19)=-3.75, P > 0.25). Still, these increases remained well within the 'neutral' zone (< 15-20°). The results suggest that among the three keyboard designs, the Comfort keyboard was the most effective in maintaining a neutral wrist posture. Although the Truform significantly reduced ulnar devation, it also yielded extension values beyond the neutral range (> 15°). Clinically, these findings may assist occupational therapists in suggesting appropriate keyboard designs during workstation ergonomic modification or consultation. Further research is needed to reinforce these findings.