Motivational determinants of physical activity in patients diagnosed with coronary artery disease

In patients with coronary artery disease (CAD), physical activity has a positive impact on physiological and psychological health. Despite the clear benefits of regular physical activity (PA) on recovery from CAD and overall health, only a small proportion of cardiac patients are active enough to derive any health benefits. While some cardiac patients might attain adequate levels of PA without assistance, research suggests that most inactive people will remain sedentary without intervention. Unfortunately, of patients who participate in exercise-based cardiac rehabilitation programs, 25% to 50% withdraw within the first six months (Oldridge, 1988, 1991; Oldridge, Dormer, & Buck, 1983; Radtke, 1989) and less than 25% of the dropouts continue an activity program sufficient to maintain or improve cardiorespiratory fitness (Radtke, 1989). This suggests that many individuals who engage in organized exercise programs are not motivated to self-regulate their PA behaviour. To promote adherence to regular PA in the cardiac patient population, an understanding of the factors, both interpersonal and interpersonal, underlying the regulation of PA behaviours is required. Theoretical frameworks are needed to link these factors and to identify change agents and targets suitable for intervention in this population. The purpose of the present thesis was to test a motivational model of physical activity regulation in patients with CAD. The Self-Determination Theory (SDT; Deci & Ryan, 1985a, 2000a), a theory of human motivation found to be useful in explaining regulation of health behaviors, was used to relate the various model components. The model links intra- and inter-personal antecedents and consequences of self-determined and non-self-determined motivation (regulatory styles) to predict physical activity regulation directly and indirectly through mediator variables. The present thesis is comprised of two studies designed to test the hypothesized model and verify the overarching role of motivational style in the successful regulation of physical activity behaviours. In the first study physical activity intentions were modelled using a correlational design. Participants diagnosed with CAD completed a one-time questionnaire at the time of admission into hospital or while participating in a hospital-based rehabilitation program. The second study employed a prospective, longitudinal design to predict physical activity behaviour in CAD patients six months after admission to hospital for a CAD diagnosis. Baseline information was collected at time of recruitment, and follow-up data was collected at 2 and 6 months after study intake. Structural equation modeling was used to test the models. Results of the two studies showed that the motivational model reliably predicted self-regulation of PA behavior. That is, the model, consisting of intra- and inter-personal variables, explained a relevant amount of variance in both physical activity intentions and behaviour. In particular, self-determined modes of motivation, at both the general and contextual levels, were found to be pivotal in the successful regulation of physical activity behaviour. The implications of the findings of this thesis research are discussed in relation to the SDT, as well as the design and implementation of exercise-based cardiac rehabilitation programs to facilitate long-term adherence to regular physical activity in the cardiac patient population