Validity and reproducibility of self-reported total physical activity--differences by relative weight.

OBJECTIVE: Physical activity is hypothesized to reduce the risk of obesity and several other chronic diseases and enhance longevity. However, most of the questionnaires used measure only part of total physical activity, occupational and/or leisure-time activity, which might lead to misclassification of total physical activity level and to dilution of risk estimates. We evaluated the validity and reproducibility of a short self-administered physical activity questionnaire, intended to measure long-term total daily 24 h physical activity.
METHOD: The questionnaire included questions on level of physical activity at work, hours per day of walking/bicycling, home/household work, leisure-time activity/inactivity and sleeping and was sent twice during one year (winter/spring and late summer). Two 7-day activity records, performed 6 months apart, were used as the reference method. One-hundred and eleven men, aged 44-78, completed the questionnaire and one or two activity records. The physical activity levels were measured as metabolic equivalents (MET)xh/day.
RESULTS: Spearman correlation coefficient between total daily activity score estimated from the first questionnaire and the records (validity) was 0.56 (deattenuated) and between the first and the second questionnaire (reproducibility) 0.65. Significantly higher validity correlations were observed in men with self-reported body mass index below 26 kg/m(2) than in heavier men (r=0.73 vs r=0.39).
CONCLUSIONS: This study indicates that the average total daily physical activity scores can be estimated satisfactorily in men using this simple self-administered questionnaire.