The Theory of Planned Behaviour and exercise: Evidence for the moderating role of past behaviour

Objectives. This study reports an application of the Theory of Planned Behaviour (TPB) to the prediction of exercise intentions and behaviour over a G-month period. The study also considers the moderating effect of past behaviour on the intention-behaviour and perceived behavioural control-behaviour relationships. Design and methods. A sample of 87 patients attending health promotions clinics in a primary care setting completed questionnaires on the TPB and exercise behaviour after their clinic appointment and were followed-up at 6 months. Results. The TPB was found to be predictive of initial exercise intentions and future exercise behaviour at 6-month follow-up, with the perceived behavioural control construct emerging as the sole independent predictor in both cases. Past behaviour was found to have a direct effect on future exercise behaviour over and above the influence of the TPB. In addition, past behaviour moderated the perceived behavioural control-behaviour relationship which was found to be significant when the frequency of past behaviour was moderate or high, but non-significant when the frequency of past behaviour was low. Conclusion. The results highlight (1) the importance of the perceived behavioural control construct of the TPB in the prediction of exercise intentions and behaviour, and (2) the need to consider the moderating effect of past behaviour on TPB-behaviour relations.