Caffeine reverts loss of muscular performance during the early-follicular phase in resistance-trained naturally menstruating women

The aim of this study was to compare the effects of caffeine ingestion on muscular performance during the early-follicular and mid-luteal phases of the menstrual cycle. Fourteen resistance-trained naturally menstruating women performed countermovement jump (CMJ), maximal voluntary isometric contraction (MVIC), one-repetition maximum (1-RM), and repetitions-to-failure (RF) at 80% of 1-RM in the half-squat exercise, in early-follicular and mid-luteal phases, after placebo or caffeine ingestion. The early-follicular and mid-luteal phases were identified via calendar-based counting method. The MVIC was lower in the early-follicular than mid-luteal phase (-6.2 +/- 15.2 N, p < 0.05) and higher with caffeine than placebo ingestion regardless of the menstrual cycle phase (+16.8 +/- 26.7 N, p < 0.05). The magnitude of gains (supplement x phase interaction, p < 0.026) in 1-RM, CMJ, and RF with caffeine ingestion was higher in the early-follicular (+16.6 +/- 7.1 kg, +2.5 +/- 1.6 cm, and +4.5 +/- 2.6 repetitions, respectively) than in the mid-luteal phase (+7.7 +/- 4.8 kg, +1.5 +/- 2.0 cm, and +2.4 +/- 3.1 repetitions, respectively). In conclusion, the greater ergogenic effect of caffeine during the early-follicular phase supports its use to mitigate the decline in muscular performance in this phase of the menstrual cycle.

Automated summary

This study aimed to compare the effects of caffeine ingestion on muscular performance during different phases of the menstrual cycle, and found that caffeine can improve muscle strength and mitigate the decline in muscular performance.