PubMed1994
This paper is a summary of several papers published in different journals and conference proceedings. The contents deal with the incidence of load related musculoskeletal illness of female workers exposed to various workloads. Furthermore, the changes in workload due to improved workplace design and the effect on the incidence of musculoskeletal illness was evaluated. The sick-leave due to musculoskeletal illness was reduced from 5.3% to 3.1% and the reduction in turn-over from 30.1% to 7.6%. The cost and the benefits of this ergonomic intervention were analysed, and showed that an investment of NOK. 350,000 produced total savings of NOK. 3,200,000. Postural load was assessed by recording electromyography (EMG) on the upper part of musculus trapezius, postural angles of the upper arm and flexion/extension of the head and back. A quantitative relationship was found between the static trapezius load and the development of musculoskeletal sick-leave, related to the length of employment. Indications were found that certain factors were associated with reduced incidence of musculoskeletal illness. These were: increasing the number and total duration of trapezius load below 1% to 2% MVC (Maximum Voluntary Contraction); reducing the magnitude of flexion angle of the upper arm in the sagittal plane and distributing the work between flexors and extensors; and a more dynamic work pattern of the upper arm. The relationship between postural load and musculoskeletal injury was studied in comparable groups of female workers with respect to age, working hours per day and time of employment. Psychosocial problems, spare time activities and living habits of the workers did not show any significant differences across the groups. The results from this study indicate that: the static trapezius load must be kept at a minimum; a median arm flexion should be less than 15 degrees and a median arm abduction less than 10 degrees. These values seem roughly to approach an acceptable arm position; and a forward median flexion of the back of less than 20 degrees seems not to lead to a higher rate of low back pain for workers with long periods of employment.