“Given physiological differences that could uniquely impact creatine utilization in females, such as creatine kinase activity across the menstrual cycle, there is potential for sex-specific differences in creatine monohydrate supplementation to influence exercise and recovery outcomes,” researchers from the Applied Physiology Laboratory at the University of North Carolina (UNC) at Chapel Hill wrote in the journal Nutrients.
The study evaluated the effect of short-term creatine monohydrate supplementation, measured by heart rate variability (as an indicator of exercise recovery) and repeated sprint performance (average power, peak power, fatigue index, time to peak power), in women across the follicular and luteal phases of their cycles.
The effects of creatine in women
This latest research builds on a 2021 review led by Dr. Abbie Smith-Ryan, director of the Applied Physiology Laboratory at UNC, that explored the use of creatine in females across the lifespan with a focus on performance, body composition, mood and dosing strategies.
According to this initial review, females have 70 to 80% lower endogenous creatine stores (produced in the liver, kidneys and pancreas) and reportedly consume significantly lower amounts of dietary creatine (from red meat, seafood and animal milk) than males.
The research team also noted that although females may not experience the same ergogenic benefits of creatine supplementation as males, the current body of literature suggests a low risk-to-benefit ratio, with most studies pointing to numerous metabolic, hormonal and neurological benefits in women.
“Creatine supplementation improves anaerobic performance and recovery; however, to date, these outcomes have not been well explored in females,” they wrote. “Reports indicate that females are the largest group of dietary supplement consumers, emphasizing the need to better understand the sex-specific effects of dietary supplements and the role of female physiology.”
The Smith-Ryan lab published another study earlier this year examining the effects of creatine loading on body mass and changes in fluid distribution across menstrual phases.
This latest randomized, double-blind, crossover study analyzed the effects of creatine monohydrate supplementation compared to a non-caloric placebo in a group of 39 active women. Participants consumed 5 g doses four times a day of their allotted test substance for five consecutive days and completed a minimum four-week washout period between their supplementation periods. German supplement manufacturer AlzChem donated the Creapure-branded creatine used in the study.
The research team collected anthropometric measurements at rest and after participants completed a repeated sprint cycling test of 10 six-second maximal sprints in the follicular (low hormone beginning on days 2–8) and luteal (high hormone beginning on days 14–18) phases.
“For repeated sprint outcomes, there was a significant phase × supplement interaction for fatigue index, with the greatest improvement seen in high hormone in the creatine monohydrate group compared to changes in the PL group,” the researchers reported.
Though not statistically significant, the data also suggested that creatine monohydrate could help counteract sprint performance decrements in the high hormone phase. It did not appear to influence heart rate variability, however, at rest or postexercise.
The researchers noted that this data can help inform creatine monohydrate loading strategies for active females but that more research is needed on the effect of longer creatine monohydrate supplementation on performance and recovery across different hormonal profiles.
“The Effects of Creatine Monohydrate Loading on Exercise Recovery in Active Women throughout the Menstrual Cycle”
Authors: Amanda N. Gordon et al.