Determinants of physical activity behaviour change in a community-based sample of middle-aged women: Integrating concepts from the theory of planned behaviour and self-determination theory

Despite numerous benefits associated with regular physical activity, the majority of North American women remain insufficiently active. Accordingly, researchers have examined a multitude of variables associated with women's physical activity participation. Two theoretical frameworks that may be extended to predict women's physical activity behaviour are the Theory of Planned Behaviour and Self-Determination Theory. This thesis examined physical activity behaviour change in a community based-sample of middle-aged women by integrating concepts from these two conceptual frameworks. Specific objectives were (1) to examine the relative influence of social support, TPB variables, and SDT variables on intentions to increase physical activity; (2) to assess the relative influence of intentions and motivation on physical activity behaviour change over time by testing mediating and moderating models; and (3) to examine relationships among barriers, environmental characteristics, and change in physical activity behavior. To these ends, two empirical investigations were conducted. In the first study, French-speaking women (n=109) completed a questionnaire package assessing the aforementioned variables. In the second study, English-speaking women (n=149) complete similar questionnaire packages at baseline and at six months follow-up. All women were recruited from community-based facilities, including community centres and fitness clubs. Overall, results demonstrated that attitudes, perceived behavioural control, subjective norms, and autonomous motivation were associated with intentions to increase physical activity. Intentions were also related to reported physical activity behaviour change over time. Among the most commonly reported barriers to physical activity increase were daily activities and fatigue. Inactive women reported higher levels of barriers than women who remained active or increased their physical activity level over time. Environmental characteristics (e.g., enjoyable scenery and the presence of others exercising) were also associated with change in physical activity behaviour. Collectively, results support the utility of integrating concepts from different theoretical frameworks as a means of understanding physical activity behaviour change and physical activity behaviour change intentions. Findings also suggest a number of ways in which physical activity behaviour change could be fostered in middle-aged women