Elements of Ergonomics Programs A Primer Based on Workplace Evaluations of Musculoskeletal Disorders

The sites were offices in two State governmental agencies in which more than 500 workers performed data entry tasks using VDTs. Questionnaires administered to the total sample of workers indicated a significant prevalence of constant musculoskeletal discomfort, with the greatest number localized to the trunk area, followed by the neck, buttocks, arm/shoulders (particularly on the right side), and, lastly, the lower legs. The specific design features of 40 workstations, representing a subsample of those used by this worker group, were analyzed to determine the extent to which they could account for the complaints. In all cases, the keyboard in these units was positioned immediately in front of the worker, with the document placed either to the left or right or between the keyboard and the display. Documents were manipulated mostly with the left hand, with the right hand used exclusively for keyboard operation. Wrist rests were not available, and flexibility in keyboard and video display placements was limited. Work tables and chairs lacked adjustable features. Various measurements and observations were made at these workstations during actual VDT work, including seat pan heights and compression seat back height, keyboard height, seated postures of the workers, upper arm angles, document distances, head tilt, gaze angle, and chair tilt and swivel. Statistical techniques were used to predict the amount of musculoskeletal discomfort from the aforementioned ergonomic variables. This analysis was performed by the region of the body affected and indicated the ergonomic factors, both singly and in combination, that could account for significant amounts of the reported discomfort in that area. The results showed, for example, that leg discomfort increased when the lower leg length exceeded the seat pan height and when the seat pan was soft. With regard to arm/shoulder discomfort, height discrepancy between the positions of the elbow and the keyboard proved to be a significant predictor as did long reaches to documents with the left arm. Less neck and trunk discomfort was found for erect sitting postures compared with stooped or slouched positions and as the height of the backrest was lowered in relation to the length of the operator's back. These and other findings served as the basis for offering suggestions about workstation configurations that could alleviate the discomfort problems [Sauter et al. 1991].