The 28-day hormonal arc and what it touches
A typical menstrual cycle averages around 28 days but normally ranges from roughly 21 to 35. It is driven by shifting estrogen and progesterone: estrogen rises through the follicular phase and peaks near ovulation, then progesterone dominates the luteal phase. These hormones influence more than reproduction, with plausible effects on substrate use, fluid balance, core temperature, recovery, and how training feels day to day.
Cycle-based periodization is a popular idea, but the controlled evidence is mixed. Many studies find small or inconsistent average differences in performance across phases, so blanket prescriptions should be treated cautiously.
Fueling and individual tracking
Practically, the most defensible approach is to fuel adequately across the whole cycle, pay attention to symptoms, and use personal logging (energy, strength, sleep, soreness) to spot real individual patterns rather than assuming the textbook curve applies. Underfueling can disrupt the cycle itself, a marker that training and nutrition are out of balance.
This is general educational information, not medical advice. Missed or irregular periods, or training amenorrhea, warrant evaluation by a qualified clinician.