The menstral cycle is really, really complex. So they're multiple hormons going on. Astrogen and pregestrone are the two main hormons here. At the beginning of the cycle, your body tends to prefer to metabl carbs. And then towards the end, during the ludial phase, when both hormone levels are high, the body is less resilient to stress. But how can that knowledge change training? One possible actic is a coach adjusts the intensity, the volume, the type of exercise depending on where an athlete is in her cycle.