Objectives: The purpose of this study was to estimate the different components of variance in exposure to nonneutral trunk postures.
Methods: The percentages of worktime spent in trunk flexion and trunk rotation or lateroflexion during 10-min observation periods were used as primary measures in analyses of variance to separate the total variance in its components. For two occupational groups six observation periods were selected per worker, and for four other groups 10 periods were used. Most of the 35 subjects were not restricted to one workplace, and they performed dynamic work while being observed.
Results: The variance within workers contributed around 80% to the total variability of exposure to both unfavorable postures. These results indicate that it is difficult to achieve an unbiased estimate of exposure to postural stress for individual workers who perform dynamic tasks in varying work situations.
Conclusions: The results indicate that it is difficult to achieve an unbiased estimate of exposure to postural stress for individual workers who perform dynamic tasks in varying work situations. Measurement strategy for exposure assessment requires many repeated observations per worker.