Effect of caffeine supplementation on physical performance in a 5 km cycling time trial of healthy young adult women in different phases of the menstrual cycle: A parallel, randomized, double-blind, placebo-controlled clinical trial.

This article investigates the effects of caffeine supplementation and menstrual cycle (MC) phase on the 5-km cycling time trial performance of female exercise practitioners (FEP). In a double-blind, randomized, placebo-controlled clinical trial involving 21 women aged 18–35 with regular menstrual cycles, participants ingested caffeine (6 mg/kg) or placebo during the late follicular and mid-luteal phases before performing the cycling test. The study found no significant impact of either caffeine supplementation or MC phase on time trial duration, mean power output, respiratory quotient, or oxygen consumption. These results suggest that, under the conditions tested, caffeine and hormonal fluctuations across these MC phases do not influence short-duration cycling performance in women.