Convergent Validity of a Physical Activity Questionnaire against Objectively Measured Physical Activity in Adults

Traditionally, a self-reported questionnaire has been a cost-effective method of gathering information about physical activity (PA). Recently, however, the use of an objective measure, such as a pedometer, has been the focus of PA studies because it permits more accurate quantification. And it can be used to validate the findings of a PA questionnaire in a large population. The objective of this study was to determine the convergent validity of a PA questionnaire against objectively measured PA in adults obtained with the use of a pedometer. 

In the study, data from the Cardiovascular Risk in Young Finns Study (YFS) were collected from 1853 participants aged 30 - 45 years old. 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. And convergent validity analyses were performed by comparing means and standard deviations of daily total steps and aerobic steps and weekly minutes of aerobic steps and their intensity (steps per minute) in three categories of leisure-time PAI.

The results indicated that 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).

In conclusion, these findings suggest that the YFS PA questionnaire is an acceptably valid subjective measure of lifestyle PA in Finnish adults and the practical advantages of its self-reporting will assure its continued use.

Article by Mirja Hirvensalo, et al, from Finland, Australia and the Netherlands.

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