The effect of imposed and self-selected computer monitor height on posture and gaze angle.

OBJECTIVE:: The objectives were to determine the postural consequences of varying computer monitor height and to describe self-selected monitor heights and postures. DESIGN:: The design involved experimental manipulation of computer monitor height, description of self-selected heights, and measurement of posture and gaze angles. BACKGROUND: Disagreement exists with regard to the appropriate height of computer monitors. It is known that users alter both head orientation and gaze angle in response to changes in monitor height; however the relative contribution of atlanto-occipital and cervical flexion to the change in head rotation is unknown. No information is available with regard to self-selected monitor heights. METHODS: Twelve students performed a tracking task with the monitor placed at three different heights. The subjects then completed eight trials in which monitor height was first self-selected. Sagittal postural and gaze angle data were determined by digitizing markers defining a two-dimensional three-link model of the trunk, cervical spine and head. RESULTS: The 27 degrees change in monitor height imposed was, on average, accommodated by 18 degrees of head inclination and a 9 degrees change in gaze angle relative to the head. The change in head inclination was achieved by a 6 degrees change in trunk inclination, a 4 degrees change in cervical flexion, and a 7 degrees change in atlanto-occipital flexion. The self-selected height varied depending on the initial monitor height and inclination. CONCLUSIONS: Self-selected monitor heights were lower than current 'eye-level' recommendations. Lower monitor heights are likely to reduce both visual and musculoskeletal discomfort. RELEVANCE: Musculoskeletal and visual discomfort may be reduced by placing computer monitors lower than currently recommended.