Questionnaires vs observational and direct measurements: a systematic review

Background: Physical work requirements can be estimated by several different methods, each with its own advantages and disadvantages. To reduce the occurrence of work-related musculoskeletal disorders, a quantitative assessment of work-related, physical risk factors is needed. Objective: To examine the validity of self-administered questionnaires (SAQ) in assessing work-related physical demands when compared to an expert's evaluation using observational and/or direct measurement. Methods: An online search of relevant databases was conducted and identified articles were critically appraised using a quality scoring checklist. Evidence from the studies was compared and summarized. Results: A total of 12 studies evaluating work-related force, duration and frequency were identified. A critical appraisal checklist was used to assess methodological quality. The majority of the studies lacked the necessary elements of measurement validity and reliability as demonstrated by their low quality scores. Overall, there was a low-to-moderate agreement between SAQ and observational/direct measurement. Conclusion: The validity of SAQ to assess work-related physical variables is questionable. When the rules of psychophysics are combined with a calibration method the validity is greatly improved. In addition, several personal factors need to be considered during data collection, in particular the presence of previous musculoskeletal disorders.