The effects of video display terminal height on the operator: a comparison of the 15 degree and 40 degree recommendations.

Prolonged use of video display terminals (VDTs) has been shown to be a risk factor for musculoskeletal and visual discomfort. A standard workplace design recommendation is to position the centre of the VDT 15 degrees below horizontal eye level. Recently a viewing angle of 40 degrees below horizontal has been suggested based on studies that have indicated that this is the preferred viewing angle for visually intensive tasks. The goal of this study was to investigate the effects of these two VDT positions on muscular activity, muscular fatigue, head/neck posture, visual acuity, operator performance (productivity and quality), heart rate and operator subjective assessment. The experimental task consisted of reading text from a computer screen and answering reading comprehension questions using a mouse and a keyboard. Each experimental session lasted 2 h. The 40 degree VDT position showed significantly greater head tilt angles and higher muscle activity levels for six of the 10 neck, shoulder and back muscles sampled. No significant differences in visual acuity, operator performance or heart rate were detected as a result of monitor location. Seven of the 12 subjects preferred the 15 degree monitor position.