Caffeine is a popular, well-studied, and effective ergogenic aid. However, the vast majority of the available trials have been conducted in men, and most of the interventions that have been conducted in women tested the ergogenic properties of caffeine during the follicular phase of the menstrual cycle, which possibly minimized the potential effects of hormonal variations on a given study’s performance outcomes (speed, strength, etc).
The menstrual cycle
Adapted from Draper et al. Sci Rep. 2018.[1]
Only one study has looked at the relationship between menstrual cycle phase and caffeine’s ergogenic effect, and it found that caffeine yielded similar effects regardless of the participants’ menstrual phase.[2]