Theory of Planned Behaviour over an exercise program in adults with and without chronic disease

Abstract

Background: The purpose of this study is to use the Theory of Planned Behaviour (TPB) model to explore differences in predictors of physical activity (PA) over time for adults with and without a chronic disease during an exercise program. Methods: Adult participants with (n=103) and without (n=155) a chronic disease (e.g., diabetes, asthma), as indicated by PAR-Q form, began a year-long exercise program. Enrolled participants completed assessments of TPB constructs (affective attitudes, instrumental attitudes, descriptive norms, injunctive norms, perceived behavioural control [PBC], intentions) and self-reported PA behaviour at baseline, 3, 6, 9, and 12 months. A path analysis comparing adults with and without a chronic disease was conducted to test the TPB model at each individual time point. Findings: PBC was the strongest predictor of intentions in adults with and without a chronic disease across all time points (β’s .26-.60). At baseline and 3 months, intentions predicted PA in adults with a chronic disease only (β’s=.19 and .23, respectively), and PBC predicted PA in the adults without a chronic disease only (β’s=.30 and .30, respectively). At 9 and 12 months, PBC was the strongest predictor of behaviour in both groups (β’s .29-.49). Discussion: In adults without a chronic disease, PBC was directly related to behaviour across all time-points. In adults with a chronic disease, intention was the strongest predictor of PA until 3 months and then PBC became a stronger correlate of PA. The changing influence of these constructs for participants with and without a chronic disease will be discussed.