The Role of Exercise Self-Efficacy in Exercise Participation Among Women With Persistent Fatigue After Breast Cancer: A Mixed-Methods Study.

OBJECTIVE: Survivors of breast cancer with persistent cancer-related fatigue (CRF) report less exercise participation compared with survivors of breast cancer without CRF. Although CRF predicts other domains of self-efficacy among survivors, the effect of CRF on exercise self-efficacy (ESE)-an important predictor of exercise participation-has not been quantified. This study examined the relationship between CRF, ESE, and exercise participation and explored the lived experience of engaging in exercise among survivors of breast cancer with persistent CRF. METHODS: Fifty-eight survivors of breast cancer (3.7 [SD = 2.4] years after primary treatment) self-reported CRF, ESE, and exercise participation (hours of moderate-intensity exercise per week). Regression and mediation analyses were conducted. Survivors who reported clinically significant CRF and weekly exercise were purposively sampled for 1-on-1 interviews (N = 11). Thematic analysis was performed across participants and within higher versus lower ESE subsets. RESULTS: Greater CRF predicted lower ESE (ß = -0.32) and less exercise participation (ß = -0.08). ESE mediated the relationship between CRF and exercise participation (ß = -0.05, 95% CI = -0.09 to -0.02). Qualitative data showed that survivors of breast cancer with higher ESE perceived exercise as a strategy to manage fatigue, described self-motivation and commitment to exercise, and had multiple sources of support. In contrast, survivors with lower ESE described less initiative to manage fatigue through exercise, greater difficulty staying committed to exercise, and less support. CONCLUSIONS: Survivors of breast cancer with persistent CRF may experience decreased ESE, which negatively influences exercise participation. Clinicians should screen for or discuss confidence as it relates to exercise and consider tailoring standardized exercise recommendations for this population to optimize ESE. This may facilitate more sustainable exercise participation and improve outcomes. IMPACT: This study highlights the behavioral underpinnings of CRF as a barrier to exercise. Individualized exercise tailored to optimize ESE may facilitate sustainable exercise participation among survivors of breast cancer with CRF. Strategies for clinicians to address ESE are described and future research is suggested. LAY SUMMARY: Women with fatigue after breast cancer treatment may have lower confidence about their ability to engage in exercise. Individually tailoring exercise to build confidence as it relates to exercise may result in more consistent exercise and better health-related outcomes.

Persistent cancer-related fatigue after breast cancer treatment predicts postural sway and post-exertional changes in sit-to-stand strategy.

Background: Chemotherapy-induced peripheral neuropathy (CIPN) is considered a primary mechanism of imbalance among women diagnosed with breast cancer. Recent evidence, however, suggests that cancer-related fatigue (CRF) may also influence balance. Purpose: Examine the contributions of CRF and CIPN to static and dynamic balance before and after a period of fatiguing exercise. Methods: This is a secondary analysis of data examining functional differences between women with breast cancer with and without persistent CRF. Postural sway was measured during static standing and the rising phase of an instrumented sit-to-stand (ISTS) before and after exercise. Regression analyses were performed to determine how CRF and severity of CIPN predicted sway and how much variance was attributable to each. Results: Greater CRF predicted increased pre-, p=.04, and post-exertional, p=.02, static sway in the anterior-posterior plane. CRF accounted for 10.5% and 9.5% of the variance in pre- and post-exertional sway (respectively) compared to the 0.9% and 1.4% accounted for by CIPN severity which was not a significant predictor. After exercise, greater CRF predicted smaller, more conservative, anterior weight shifting during the ISTS, p=.01, and accounted for 6.6% of the variance in sway compared to 3% attributed to CIPN which was not a significant predictor. Limitations: This analysis is limited by its small and demographically homogenous sample. Conclusions: These results suggest that CRF may influence balance independent of CIPN symptoms. While CIPN remains a risk factor for imbalance in this population, CRF warrants consideration in clinical practice and research as a mechanism of postural instability.