The Theory of Planned Behaviour predicts objectively measured walking behaviour in a general public sample, but not change in objectively measured walking

Background: Previous research has demonstrated Theory of Planned Behaviour (TPB) variables as consistent predictors of physical activity intentions and behaviour. Other studies have shown that TPB variables do not predict objectively measured physical activity, but there were limitations in sample and method in these studies. The present study aimed to assess which TPB variables predicted objective walking behaviour, and change in objectively measured walking behaviour, in a general public sample. Methods: N=315 patients were recruited from general practices as part of a randomised controlled trial. Patients completed TPB questionnaire measures at baseline, immediately post-intervention, at six weeks and six months follow-up. Patients wore a New Lifestyles NL-1000 pedometer at each time point. Multiple hierarchical regression analyses were conducted. Findings: TPB variables explained 42 per cent of the variance in intentions immediately post-intervention, 51 per cent of the variance at six weeks, and 43 per cent at six months. Prediction of objective walking behaviour by intention and PBC was not demonstrated post-intervention, but explained 5.8 per cent of unique variance at six weeks, and 5.9 per cent at six months. When past behaviour was controlled for, the TPB variables failed to predict change in objective walking behaviour. Discussion: TPB variables are predictive of intentions and objective walking behaviour, but not behaviour change, in the current sample. Past behaviour was the most important predictor of future behaviour, therefore suggesting walking is a habitual behaviour. In contrast to previous reports, the TPB does predict objectively measured walking behaviour when appropriate TPB measures and samples are used. Implications for intervention development are discussed.