Single-Case Experimental Design to Assess a Physical Activity Intervention on Daily Self-Efficacy in Women with Breast Cancer and Psychological Distress

During a physical activity (PA) intervention, improving self-efficacy is a major step to help patients with breast cancer (BC) to modify their PA behavior and improve their physical and psychological health. It appears crucial to examine how self-efficacy fluctuate at an individual level and if emotional and physiological states influence it. We conducted a series of N-of-1, with an ABA’ design, to examine the effects of a 12-week PA intervention on daily self-efficacy level among women with BC and severe psychological distress. Phase A and A’ (2 weeks each) represented pre- and post-intervention measures. During the 16 weeks of the study, 16 participants daily reported their self-efficacy, depression, and anxiety levels. Self-efficacy changed over time in a pattern that was specific to each individual. A significant increase of self-efficacy has been found for 10 participants during and/or after the intervention phase. Thus, timing and content of future self-efficacy enhancement intervention should be personalized in future studies.