Does the menstrual cycle affect caffeine’s performance-enhancing properties?

Caffeine is a popular ergogenic aid, the use of which is highly prevalent^[1] among athletes, with roughly three out of four athletes regularly using caffeine since 2004, when it was removed from the World Anti-Doping Agency list of banned substances. The ergogenic effects of caffeine have been studied for over 100 years, with the first known study^[2] on caffeine and exercise performance published in 1907.

A number of meta-analyses investigating the effects of caffeine consumption on exercise performance have been conducted to date. These meta-analyses have explored the effects of caffeine on different aspects of exercise performance, including aerobic endurance^[3], muscle strength^[4], muscle endurance, and anaerobic power^[5], and have found that caffeine is, indeed, an effective ergogenic aid.

While the results from the majority of the research generally confirm caffeine’s ergogenic properties, this research is characterized by the very same focus on male participants that plagues the related literature as a whole. Although trials that have recruited women suggest that caffeine has similar^[6] performance-enhancing effects in men and women, in most of these trials, the ergogenic effects of caffeine were examined during the follicular phase of the menstrual cycle, shown in Figure 1. This was likely done in order to minimize the potential effects of variations in female sex hormones during the menstrual cycle.

Since variations in female hormones may be able to influence the effect of caffeine on increasing blood pressure^[7] and enhancing mood^[8], and as the phase of the menstrual cycle can interfere^[9] with the speed of clearance of caffeine from the body, it’s possible that the magnitude of the ergogenic effect of caffeine may vary during the different phases of the menstrual cycle. However, no research to date has investigated these potential interactions. The study under review was the first to examine the ergogenic effects of caffeine ingestion in women during three different phases of the menstrual cycle (early follicular, preovulatory, and mid-luteal).

Caffeine is a popular ergogenic aid, the use of which is highly prevalent among athletes. While the results from most of the research generally confirm caffeine’s performance-enhancing properties, the vast majority of the available trials have been conducted in men. Moreover, most of the interventions that have been conducted in women have tested the ergogenic properties of caffeine during the follicular phase of the menstrual cycle. While it’s possible that the magnitude of the ergogenic effect of caffeine may vary during the different phases of the menstrual cycle, no research to date has investigated these potential interactions. The study under review was the first to examine the ergogenic effects of caffeine ingestion in women during three different phases of the menstrual cycle.