In response to a considerable degree of concern expressed about the safety of video display terminals (VDTs) for the user, an experiment was conducted in which five sessions of 3 hours each of VDT operation were planned. In each session the operator worked under conditions which alternated between good and poor as concerned working and seating surfaces, lighting, and glare. Measurements were taken of performance during each session and psychophysical/physiological measurements and subjective complaints were recorded. The subjects of the study were 13 volunteers with no prior VDT operation experience. In the worst case condition, a standard nonadjustable office chair with limited lumbar support was used. No wrist rest or copy holders were available. Adjustable work stations were deliberately set at 45 degrees from horizontal, and the screen viewing angle was 30 degrees to screen center. Glare conditions were created as well. The character/screen contrast ratio was only slightly better than 1:1, with an illuminance value of 1081 lux on the hard copy. These conditions were similar to many discovered in the actual working world. When working conditions were made better during the course of the study, a 24.5 percent improvement in task performance was noted along with a decrease in musculoskeletal complaints.
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