Questionnaire versus direct technical measurements in assessing postures and movements of the head, upper back, arms and hands

Objectives This study compares questionnaire-assessed exposure data on work postures and movements with direct technical measurements. Methods Inclinometers and goniometers were used to make full workday measur ements of 41 office workers and 41 cleaners, stratified for such factors as musculoskeletal complaints. The subjects answered a questionnaire on work postures of the head, back, and upper arms and repealed movements of the ar ms and hands (3-point scales). The questionnaire had been developed on the basis of a previously validated one. For assessing worktasks and their dura tions, the subjects kept a 2-week worktask diary. Job exposure was individu ally calculated by time-weighting the task exposure measurements according to the diary. Results The agreement between the self-assessed and measured postures and m ovements was low (kappa = 0.06 for the mean within the occupational groups and kappa = 0.27 for the whole group). Cleaners had a higher measured workl oad than office workers giving the same questionnaire response. Moreover, t he subjects with neck-shoulder complaints rated their exposure to movements as higher than those without complaints but with the same measured mechani cal exposure. In addition, these subjects also showed a general tendency to rate their postural exposure as higher. The women rated their exposure hig her than the men did. Conclusions The questionnaire-assessed exposure data had low validity. For the Various response categories the measured exposure depended on occupatio n. Furthermore, there was a differential misclassification due to musculosk eletal complaints and gender. Thus it seems difficult to construct valid qu estionnaires on mechanical exposure for establishing generic exposure-respo nse relations in epidemiologic studies, especially cross-sectional ones. Di rect technical measurements may be preferable.