Breast cancer (BC) is one of the most common cancers in the United States. Advances in detection and treatment have resulted in an increased survival rate, meaning an increasing population experiencing declines in muscle mass and strength. Creatine supplementation has consistently demonstrated improvements in strength and muscle performance in older adults, though these findings have not been extended to cancer populations.

Purpose: The purpose of this study was to investigate the effects of short-term creatine supplementation on muscular performance in BC survivors.

Methods: Using a double-blind, placebo-controlled, randomized design, 19 female BC survivors (mean ± SD age = 57.63 ± 10.77 years) were assigned to creatine (SUPP) (n = 9) or dextrose placebo (PLA) (n = 10) groups. The participants completed two familiarization sessions, then two test sessions, each separated by 7 days, where the participants supplemented with 5 g of SUPP or PLA 4 times/day between sessions. The testing sessions included sit-to-stand power, isometric/isokinetic peak torque, and upper/lower body strength via 10 repetition maximum (10RM) tests. The interaction between supplement (SUPP vs. PLA) and time (Pre vs. Post) was examined using a group × time ANOVA and effect sizes.

Results: No significant effects were observed for sit-to-stand power (p = 0.471; η_p² = 0.031), peak torque at 60°/second (p = 0.533; η_p² = 0.023), peak torque at 120°/second (p = 0.944; η_p² < 0.001), isometric peak torque (p = 0.905; η_p² < 0.001), 10RM chest press (p = 0.407; η_p² = 0.041), and 10RM leg extension (p = 0.932; η_p² < 0.001). However, a large effect size for time occurred for the 10RM chest press (η_p² = 0.531) and leg extension (η_p² = 0.422).

Conclusion: Seven days of creatine supplementation does not influence muscular performance among BC survivors.