Goniometer measurement and computer analysis of wrist angles and movements applied to occupational repetitive work

In epidemiological studies of occupational musculoskeletal disorders there is a need for quantitative exposure measurements of the physical work load. In studies of neck and upper limb disorders the so-called cumulative trauma disorders (CTDs), in particular the carpal tunnel syndrome, the positions and movements of the wrist are of special interest. A biaxial flexible electrogoniometer was used to measure continuously, with a sampling rate of 20 Hz, wrist flexion/extension and abduction/adduction angles up to 27 min. Evaluation of the influence of rotation on the goniometer showed some inherent crosstalk, which, however, did not invalidate the results. For occupational repetitive work, 99.5% of the signal power was contained in the 0-5 Hz band. Two-dimensional angle distributions and power spectra gave comprehensive information about wrist postures and movements. Measures reflecting both static and dynamic properties were derived from time and frequency domains. These measures give quantitative information on different potential risk factors and are therefore useful in epidemiological studies. Mean power frequency (MPF) is suggested as a generalized measure of repetitiveness. The method was applied in field studies of fish processing industry workers with highly repetitive work and risk of CTD.