A longitudinal study of physical activity behaviour in chronic disease: The example of chronic obstructive pulmonary disease

In chronically ill adults, involvement in physical activity is associated with reduced mortality and better quality of life. In chronic obstructive pulmonary disease (COPD), exercise training within a pulmonary rehabilitation program leads to improvements in dyspnea, exercise capacity and quality of life measured immediately after the program. These gains diminish within 6--18 months of program completion, in part due to patients' difficulty in sustaining physical activity behaviour. The global objective of this thesis was to examine behavioural and disease-related aspects of physical activity over 1 year among individuals with COPD.;In the second study, logistic longitudinal modelling showed that adherence to exercise (≥3 days per week for endurance exercise and ≥2 days per week for strength exercise) declined progressively between 4 and 12 months after rehabilitation start. Adherence to endurance exercise was higher during spring/summer, and if individuals had exercised prior to rehabilitation (past habits); more severe airway obstruction at baseline and reporting a COPD exacerbation during rehabilitation predicted worse adherence. Greater baseline self-efficacy for carrying out strength exercise predicted better adherence to this, type of exercise.;Patterns of physical activity, defined as weekly time of endurance activity, were examined from 4--12 months in the third study. Heterogeneity was detected within the sample, as trajectory modelling identified 3 distinct sub-groups: 55% of individuals started at a low activity level and stayed low; 30% started high and stayed high; 15% started high and declined. The strongest discriminating baseline variables between sub-groups were past exercise habits, 6-minute walk distance and barriers to exercise. Individuals in the high/decline group had the greatest barriers, which are potentially modifiable.;In summary, rehabilitation programs impact positively on behavioural aspects of exercise, however adherence to exercise declines after a structured rehabilitation program when individuals must sustain the behaviour independently. There is, however, heterogeneity in physical activity patterns among patients with COPD. Results were synthesized across the 3 studies and a preliminary set of recommendations for pulmonary rehabilitation practice were developed. Recommendations emphasize that behavioural, disease-related and seasonal factors, associated with physical activity, should be addressed within rehabilitation programs through behavioural and self-management interventions. Future research will be required to develop and test these interventions.;A longitudinal behavioural study was embedded within a randomized multicentre trial comparing the effectiveness of home-based versus hospital-based outpatient pulmonary rehabilitation. The first study of this thesis assessed behavioural aspects of exercise before and after a 3-month rehabilitation program. Exercise habits, self-efficacy for exercise and barriers to exercise improved significantly following rehabilitation. In cross-sectional path analysis, past exercise habits and greater exercise capacity had a positive effect On self-efficacy for endurance exercise (measured pre-rehabilitation), while external barriers, depression and female sex had a negative effect.