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.

Abstract

Background: Although caffeine is the most studied ergogenic aid, few studies have been conducted to evaluate the effect of caffeine supplementation among women in different phases of the menstrual cycle (MC).

Aim: To verify the effect of caffeine supplementation and the MC phase on the performance of a 5 km cycling time trial of female exercise practitioners (FEP).

Methods: This was a parallel, double-blind, randomized, placebo-controlled clinical trial with a sample of women aged 18-35 years, all with regular MC. The caffeine (CAFG) and placebo (PLAG) groups performed the exercise test during the late follicular phase and mid-luteal phase. These time points were individually assessed according to each woman's MC. On the test day, they were instructed to intake a standardized meal. Subsequently, 30 min following the meal, volunteers consumed caffeine (6 mg·kg^-1) or placebo. One hour following caffeine intake, the exercise protocol started. The participants were instructed to perform an all-out 5-km cycling time trial.

Results: Twenty-one women with a mean age of 26.6 years (PLAG, n = 10; 26.7 y; CAFG, n = 11; 26.5 y) were evaluated. The mean test duration was approximately 10-min, with no effect of the MC phase (F = 0.410; p = 0.532), caffeine supplementation (F = 2.23; p = 0.156), or interaction (F = 0.298; p = 0.593). Likewise, we did not verify the effect of the MC phase (F = 0.249; p = 0.625), caffeine supplementation (F = 2.35; p = 0.146), or interaction (F = 0.585; p = 0.456) on the mean power.

Conclusion: Neither caffeine supplementation nor the different MC phases had an impact on the 5-km cycling TT performance of FEP.