Author: Yannik Guthard et al
Journal: Nature (2026)

AI generated summary

This systematic review and meta-analysis investigated whether the risk of muscle injuries varies across phases of the menstrual cycle in eumenorrheic female team-sport athletes. Following PRISMA 2020 and PERSiST guidelines, the authors reviewed literature up to January 2024 and included studies that compared muscle injury occurrence across at least two menstrual cycle phases in naturally menstruating athletes.

Only three observational studies met the inclusion criteria, comprising data from 318 female athletes competing mainly in professional football and futsal. Due to large inconsistencies in how menstrual phases were defined across studies, all data were aligned to a simplified two-phase model (follicular vs. luteal phase) for meta-analysis.

The pooled results showed no statistically significant difference in muscle injury occurrence between the follicular and luteal phases (Risk Ratio = 1.18, 95% CI: 0.75–1.86). Individual studies reported conflicting patterns, with some indicating higher injury rates in late follicular or premenstrual phases, but these findings were inconsistent and not robust when pooled.

The certainty of evidence was rated very low, primarily due to:

• Inconsistent menstrual cycle phase classification
• Reliance on self-reported or calendar-based cycle tracking rather than hormonal verification
• Limited sample size and number of studies
• Heterogeneous injury definitions and exposure metrics

As a result, no practical or clinical recommendations regarding menstrual cycle–based injury risk modulation can currently be made.

The authors conclude that while hormonal fluctuations plausibly influence musculoskeletal properties, existing evidence is insufficient to confirm a meaningful relationship with muscle injury risk. They strongly recommend future research using standardised cycle classification, physiologically accurate phase detection (e.g. hormonal assays or ovulation kits), and more granular injury data to clarify potential associations.