Weight Lifting and Physical Function among Breast Cancer Survivors: A Post Hoc Analysis of a Randomized Controlled Trial

Breast cancer survivors may experience deterioration of physical function. This is important because poor physical function may be associated with premature mortality, injurious falls, bone fracture, and disability. We conducted a post hoc analysis to explore the potential efficacy of slowly-progressive weight lifting to reduce the incidence of physical function deterioration among breast cancer survivors. Methods: Between October 2005 and August 2008, we conducted a single-blind, 12-month, randomized controlled trial of twice-weekly slowly-progressive weight lifting or standard care among 295 non-metastatic breast cancer survivors. In this post hoc analysis of data from the Physical Activity and Lymphedema Trial, we examined incident deterioration of physical function after 12-months, defined as a ≥10-point decline in the physical function subscale of the Medical Outcomes Short-Form 36-item (SF-36) questionnaire. We calculated the relative risk (RR) and 95% confidence interval (95% CI) using an unadjusted generalized linear model. Results: Study participants were 56 ± 9 years old (range 36–80). Median adherence to the weight lifting protocol was 81% over 12-months. As compared with the control group, the weight lifting group had greater improvements in upper- and lower-body strength at 12-months (both comparisons P < 0.001). The proportion of participants who experienced incident physical function deterioration after 12-months was 16.3% (24/147) in the control group and 8.1% (12/148) in the weight lifting group [RR: 0.49 (95% CI, 0.25–0.96); P = 0.04]. No serious or unexpected adverse events occurred that were related to weight lifting. Conclusion: Slowly-progressive weight lifting compared to standard care reduced the incidence of physical function deterioration among breast cancer survivors. These data are hypothesis generating. Future studies should directly compare the efficacy of weight lifting to other modalities of exercise, such as brisk walking, to appropriately inform the development of a confirmatory study designed to preserve physical function among breast cancer survivors.