Development of observational methods for estimation of exposure to workplace postural stress

Several recent studies have illustrated the need for a simple observational instrument for the estimation of exposure to postural stress in epidemiological studies of musculoskeletal disorders. Such an instrument is particularly necessary in developing countries. This paper describes the development of an observational instrument across a spectrum of industrial occupations in South Africa. The instrument was derived from adaptations to previously published observational methods and was specifically adapted to the measurement and application constraints identified during empirical development work in various industries. The final instrument fulfilled its aims of being applicable across a broad spectrum of jobs, including a broad spectrum of exposure variables and being reasonably cost- and time-effective. Some construct validity is indicated by the fact that two out of the three main exposure variables of interest showed significant associations with neck and shoulder pain in an epidemiological analysis. These variables were the score of summed estimates of the duration of time in sustained postures in a working day and the score of estimated overall repetitiveness based on cycle-time criteria. Further investigations are needed for pain at other anatomical sites. The measurement and scoring problems identified are discussed with reference to some aspects of these results.