Hormonal

Using assumed or estimated menstrual cycle phases (e.g., calendar-based counting) instead of direct biochemical verification (e.g., LH surge, progesterone levels) produces invalid and unreliable data in sport-related research.

Do not use calendar-based methods or apps to assign menstrual cycle phases in research or applied practice without biochemical verification. To accurately determine phases (e.g., follicular vs. luteal), you must measure biological markers such as urinary luteinizing hormone (LH) surges and serum/saliva progesterone levels. Relying on calendar counting alone is scientifically invalid due to high inter- and intra-individual variability in ovulation timing and the prevalence of subtle menstrual disturbances.