Abstract
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(p)(2) = 0.031), peak torque at 60°/second (p = 0.533; η(p)(2) = 0.023), peak torque at 120°/second (p = 0.944; η(p)(2) < 0.001), isometric peak torque (p = 0.905; η(p)(2) < 0.001), 10RM chest press (p = 0.407; η(p)(2) = 0.041), and 10RM leg extension (p = 0.932; η(p)(2) < 0.001). However, a large effect size for time occurred for the 10RM chest press (η(p)(2) = 0.531) and leg extension (η(p)(2) = 0.422). CONCLUSION: Seven days of creatine supplementation does not influence muscular performance among BC survivors.