Validity of occupational energy expenditure assessed by interview

Measuring physical activity at work has been a field of growing interest in recent decades, and there is a need for reliable, standardized assessment instruments for application in large population studies. The present study examined the validity of a task-oriented interview for assessing energy expenditure in occupational work. The interview was developed for use in the MUSIC-Norrtälje study, a population study with the overall aim of identifying risk and preventive factors for musculoskeletal disorders. Twenty-seven persons were included in the study. Each respondent defined all tasks performed during a typical workday and estimated their durations. For each task the interviewer then assessed the level of energy expenditure in multiples of the resting metabolic rate (MET) and calculated a time-weighted average MET (TWA-MET) for a typical workday. Measurements of oxygen consumption and observations of duration of each work task were performed during 2 workdays in all the interviewed subjects. The validity was tested by comparing TWA-MET derived from the interviews with those derived from measurements; the product moment correlation coefficient was 0.70. The interview may offer sufficient validity for assessment of energy expenditure in large population studies.