SOURCES OF VARIANCE IN EXPOSURE TO NONNEUTRAL TRUNK POSTURES IN VARYING WORK SITUATIONS

Objectives The purpose of this study was to estimate the different com ponents 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 primar y measures in analyses of variance to separate the total variance in i ts components. Far two occupational groups six observation periods wer e selected per worker, and for four other groups 10 periods were used. Most of the 35 subjects were not restricted to one workplace, and the y performed dynamic work while being observed. Results The variance wi thin workers contributed around 80% to the total variability of exposu re to both unfavorable postures. These results indicate that it is dif ficult to achieve an unbiased estimate of exposure to postural stress for individual workers who perform dynamic tasks in varying work situa tions. Conclusions. The results indicate that it is difficult to achie ve an unbiased estimate of exposure to postural stress for individual workers who perform dynamic tasks in varying work situations. Measurem ent strategy for exposure assessment requires many repeated observatio ns per worker.