Objectives: To produce evidence for factor validity and longitudinal invariance of scales used to examine the theory of planned behavior applied to physical activity.
Methods: Self-report questionnaires were administered at 3- (n = 267) and 12-months (n = 333) postpartum.
Results: A single-factor model fit data from the normative beliefs, perceived behavioral control, and behavioral beliefs scales. Attitude and control beliefs were found to be multidimensional. Longitudinal invariance of all scales was supported.
Conclusions: Each scale had strong validity evidence. Future research using these measures will help identify areas for intervention and reveal how changes in these constructs influence physical activity.