Convergent Validity of a Physical Activity Questionnaire against Objectively Measured Physical Activity in Adults: The Cardiovascular Risk in Young Finns Study

Background: Traditionally, a self-reported questionnaire has been a cost-effective method of gathering information about physical activity (PA). An objective measurement, such as the use of a pedometer, can be used to validate the findings of a PA questionnaire in a large population. Objective: The study objective was to determine the convergent validity of a PA questionnaire against objectively measured PA in adults obtained with the use of a pedometer. Methods: Data from the Cardiovascular Risk in Young Finns Study (YFS) were collected from 1853 participants aged 30 - 45 years. The participants completed a self-reported questionnaire that included items on leisure time, commuting and habitual PA. PA was expressed as leisure-time physical activity index (PAI) and metabolic equivalent hours/week (METh/wk). The participants wore a pedometer for seven consecutive days and used it to record their total daily and aerobic steps. Results: There was a low to moderate association between the self-reported questionnaire and pedometer measurements regarding both total steps and aerobic steps taken during leisure time and commuting PA. An association was not observed between pedometer data and habitual PA. Of the individual items in the questionnaire, questions that described the frequency of PA and the duration of vigorous PA correlated the most strongly with the pedometer values obtained for total and aerobic steps (r = 0.28 - 0.44, p ≤ 0.010). Conclusions: These findings suggest that the YFS PA questionnaire showed acceptable convergent validity in assessing, in particular, exercise-type PA in an adult population.