We are all governed by a circadian rhythm (day/night cycle). In addition, people who menstruate live according to an infradian rhythm (the menstrual cycle). Just as we rarely study better at 3 in the morning than at 2 in the afternoon, there are windows within the cycle that are more conducive to increasing training load, and other moments that call for more rest.
On the ground, recent work in elite contexts shows natural adjustments:
Elite cyclists and Olympians followed over several cycles; less time was spent in a high-effort state during menstruation than during the follicular or luteal phase, along with transitions in perceived exertion ("easy" → "hard").
Another study, this time multi-sport, led by Juliana Antero among elite athletes preparing for the Paris 2024 Olympic Games, revealed a peak in intensity from the day after the end of menstruation through to ovulation. It was also noted that during training, athletes covered less distance and trained at lower intensity during menstruation.
Taking your cycle into account in your training means adjusting a few key moments: more intensity at certain times and more recovery at others, and putting yourself in the best possible conditions for competition, whatever day it falls on.
You don't need to be training for a marathon to adapt your workout. Do you do a bit of sport? Track your sensations (sleep, mood, pain, overall energy) and your performance (in intensity and/or duration), sync a few key sessions with your optimal windows, and schedule recovery when your body asks for it. It will thank you ^^