Muscle Coordination and Choice-reaction Time Tests As Indicators of Occupational Muscle Load and Shoulder-neck Complaints

The use was explored of psychomotor tests as indicators of the risk of shoulder-neck disorders in workers with low-level static loads on the shoulder muscles. Two groups of workers performing office work and light production work were studied. A muscle coordination test with continuous movement of the arm and hand between three target areas and a psychogenic tension test, posing mental demands and with minimal requirement for body movements, aimed to quantify muscle activity in excess of that needed for biomechanical purposes. The electromyogram (EMG) recording of the active trapezius muscle in the muscle coordination test correlated with the median and static EMG values of the vocational (i.e. during the normal work task) trapezius recording both for the office and production workers, but showed no correlation with shoulder-neck complaints. The EMG responses in the psychogenic tension test and of the passive (contralateral) trapezius in the muscle coordination test correlated best with the parameters showing short, spontaneous pauses in the EMG recording of occupational load. For the office workers, but not for the production workers these parameters also correlated with shoulder-neck complaints and the presence of psychosocial problems. Psychomotor tests may thus be useful as indicators of the risk of shoulder-neck complaints in certain occupations, but further experimentation is needed to validate this conclusion.