Comparison of self-reported and device-based measured physical activity—a replication study

Abstract Comparing adherence to physical activity (PA) guidelines can be challenging due to the varying types of measurement and analysis methods used to quantify PA. Therefore, previous results of test–retest reliability, validity, and stability for self-reported (i.e., questionnaire and diary) and device-based measured (i.e., accelerometry with 10/60 s epochs) PA were replicated in 43 adults and 50 children from the SMART FAMILY 2.0 trial. Data were collected throughout two independent measurement weeks and descriptive values were reported and visualized. The relationships among and between all variables included during both measurement weeks for each quality criterion were analyzed using Spearman correlations, stratified by children and adults. This was done to illustrate the quality criteria, namely test–retest reliability, validity, and stability. Descriptive results showed the highest moderate and vigorous PA values for questionnaires and accelerometry showed the second highest results in moderate PA, while in vigorous PA the estimations by the diary were higher than those of accelerometry. As before, only accelerometry demonstrated preliminary evidence for reliable, valid, and stable results for both epoch lengths. Contrary to our previous findings, the diary showed higher correlation coefficients for the quality criteria than the questionnaire. Additionally, correlation coefficients were higher in moderate than in vigorous PA, and the patterns of significance differed partially between children and adults. The present results reinforce the findings and conclusions presented in the previous study and add information about PA questionnaire results in children. Comparing both studies, discrepancies exist in estimating vigorous PA in healthy adults by the Global and the International Physical Activity Questionnaire.