Abstract
Purpose: Previously, we reported the feasibility and preliminary efficacy of an internet-delivered physical activity (PA) behaviour change program among cancer survivors. The purpose of this study was to examine effects of this program on motivation. Methods: 95 cancer survivors were randomized into either UCAN, a Theory of Planned Behaviour (TPB) based PA behaviour change program, or usual care (UC). We examined mean change (MC) in motivational outcomes and underlying beliefs from baseline to post-intervention using ANCOVAs. Results: UCAN reported lower TPB outcomes than UC. Significant negative effects were found for self-efficacy (adjusted MC -0.7; 95% CI= -1.2 to -0.1; d=-0.53, p=.019), affective attitude (AMC -0.4; 95% CI= -0.8 to -0.0; d=-0.45, p=.044), and instrumental attitude (AMC -0.5; 95% CI= -0.9 to -0.1; d=-0.43, p=.026). Significant negative effects were found among the underlying control beliefs for bad weather (AMC -0.8; 95% CI= -1.6 to -0.1; d=-0.49, p=.030), medical or health issues (AMC -0.7; 95% CI= -1.3 to -0.1; d=-0.48, p=.031), pain or soreness (AMC -0.7; 95% CI= -1.4 to -0.1; d=-0.52, p=.020), family responsibilities (AMC -1.0; 95% CI= -1.7 to -0.3; d=-0.62, p=.005), or PA becoming boring (AMC -0.8; 95% CI= -1.4 to -0.1; d=-0.54, p=.016). Conclusions: UCAN had a negative effect on motivational outcomes despite small beneficial effects on PA in the primary paper. These contradictory findings may be explained by methodological issues related to the measurement of motivation and to the specific intervention used in UCAN. Further research is needed before testing in a large scale phase III trial.Acknowledgments: This work was supported by the Canada Research Chairs Program held by Kerry Courneya.