Investigating the youth physical activity promotion model: internal structure and external validity evidence for a potential measurement model.

The purpose of the study was to investigate the measurement properties of questionnaires associated with the Youth Physical Activity Promotion (YPAP) model. Data were collected from 296 children in Grades 5-8 using several existing questionnaires corresponding to YPAP model components, a physical activity questionnaire, and 6 consecutive days of pedometer data. Internal validity of the questionnaires was tested using confirmatory factor analyses, and external validity was investigated via correlations with physical activity and body composition. Initial model fit of the questionnaires ranged from poor to very good. After item removal, all scales demonstrated good fit. Correlations with percentage body fat and objectively measured physical activity were low but in the theoretically predicted direction. The current study provides good internal validity evidence and acceptable external validity evidence for a brief set of questionnaire items to investigate the theoretical basis for the YPAP model.