Kerry S. Courneya, Kristina H. Karvinen, Margaret L. McNeely, Kristin L. Campbell, Sony Brar, Christy G. Woolcott, Anne McTiernan, Rachel Ballard-Barbash and Christine M. Friedenreich
Few studies have examined the predictors of adherence separately for supervised and unsupervised exercise or in postmenopausal women over an extended time period. Here, we report the predictors of exercise adherence in the Alberta Physical Activity and Breast Cancer Prevention (ALPHA) Trial.
The ALPHA trial randomized 160 postmenopausal women in Calgary and Edmonton, Canada to an exercise intervention that consisted of an average of 200 min/wk of supervised (123 minutes) and unsupervised (77 minutes) exercise over a 1-year period. Baseline data were collected on demographic, health-related fitness, quality of life, and motivational variables from the theory of planned behavior.
Participants completed an average of 95% of their supervised exercise and 79% of their unsupervised exercise. In multivariate analyses, 8.1% (P = .001) of the variance was explained for supervised exercise by being from Edmonton (β = 0.22; P = .004) and older (β = 0.15; P = .050). For unsupervised exercise, 21.1% (P < .001) of the variance was explained by being from Calgary (β = –0.39; P < .001), having a family history of breast cancer (β = 0.21; P = .003), and having higher vitality (β = 0.19; P = .011).
Predictors of adherence may differ for supervised and unsupervised exercise, moreover, predicting adherence to supervised exercise may be particularly difficult in well-controlled efficacy trials.
Ikuyo Imayama, Catherine M. Alfano, Caitlin E. Mason, Chiachi Wang, Liren Xiao, Catherine Duggan, Kristin L. Campbell, Karen E. Foster-Schubert, Ching-Yun Wang and Anne McTiernan
Regular exercise increases exercise self-efficacy and health-related quality of life (HRQOL); however, the mechanisms are unknown. We examined the associations of exercise adherence and physiological improvements with changes in exercise self-efficacy and HRQOL.
Middle-aged adults (N = 202) were randomized to 12 months aerobic exercise (360 minutes/week) or control. Weight, waist circumference, percent body fat, cardiopulmonary fitness, HRQOL (SF-36), and exercise self-efficacy were assessed at baseline and 12 months. Adherence was measured in minutes/day from activity logs.
Exercise adherence was associated with reduced bodily pain, improved general health and vitality, and reduced role-emotional scores (P
trend ≤ 0.05). Increased fitness was associated with improved physical functioning, bodily pain and general health scores (P
trend ≤ 0.04). Reduced weight and percent body fat were associated with improved physical functioning, general health, and bodily pain scores (P
trend < 0.05). Decreased waist circumference was associated with improved bodily pain and general health but with reduced role-emotional scores (Ptrend ≤ 0.05). High exercise adherence, increased cardiopulmonary fitness and reduced weight, waist circumference and percent body fat were associated with increased exercise self-efficacy (P
trend < 0.02).
Monitoring adherence and tailoring exercise programs to induce changes in cardiopulmonary fitness and body composition may lead to greater improvements in HRQOL and self-efficacy that could promote exercise maintenance.