An evaluation of visual display unit placement by electromyography, posture, discomfort and preference

Due to a dramatic increase in musculoskeletal disorders relating to compute r use, a number of ergonomics recommendations have been proposed in order t o combat this problem. However, some of these recommendations have been con flicting, for example, visual display unit (VDU) monitor placement. This st udy aimed to investigate the effects of monitor placement in a group of nor mal subjects. Ten male and ten female subjects within the working age range volunteered to perform a computing task for 20 min in two different VDU mo nitor placement conditions; high monitor position (HMP) and a low monitor p osition (LMP). Postural angles (gaze, head, neck, and trunk), normalised el ectromyography (upper trapezius and cervical and thoracic erector spinae), discomfort (upper body), and individual preference for monitor placement we re determined. The results indicated that the gaze, head, neck, and trunk a ngles in the LMP were significantly greater (more flexed) than those in the HMP. There was a trend for lower levels of electromyographic (EMG) activit y for trapezius in the HMP. There were significantly lower levels of EMG ac tivity for cervical and thoracic erector spinae in HMP. There was no differ ence between the monitor placement conditions on the basis of discomfort ra tings. Twelve subjects preferred the HMP compared to 7 for LMP, whilst 1 ha d no preference. The results of this study suggested that subjects may use a less flexed head, neck and trunk posture and less cervical and erector sp inae muscle activity when working with a HMP. However, the compromise betwe en musculoskeletal and visual criteria over prolonged work periods requires further research before a recommendation for VDU height can be justified. Relevance to industry Visual display units are widely used in all industries. The optimisation of their placement is a critical aspect of the human-machine interaction impa cting on worker health, satisfaction and performance. (C) 2000 Elsevier Sci ence B.V. All rights reserved.