Menstrual Cycle and Performance

The menstrual cycle matters in sport and exercise medicine (SEM) mainly through symptoms and treatable pathology, not through any proven effect of cycle phase on performance.

• •Menstrual symptoms are common, and athletes frequently report them interfering with training and competition
• •Menstrual dysfunction is one of the earliest clinical signals of low energy availability, so a cycle that stops is a finding, not a harmless result of being fit
• •Heavy menstrual bleeding is a treatable cause of iron deficiency, which limits endurance and is easy to miss if nobody asks

The evidence that cycle phase itself changes performance is much weaker than the confidence with which the subject is usually discussed. Treat the symptoms, find the treatable pathology, and do not build a training programme on an effect the data do not support. Interest also persists in whether oestradiol-driven changes in ligament laxity alter injury risk across the cycle, though that evidence is thinner still.