This article aims to clarify why, and by which mechanisms, exercise may influence the normal menstrual cycle. Therefore, the vast amount of literature on this subject is reviewed and a critical appraisal of the most widespread hypotheses is offered.
The strikingly low body mass which frequently accompanies exercise-related menstrual irregularities (ERMI) has led some authors to develop a hypothesis which postulates that a critical percentage of body fat is essential to trigger normal menstruation. The relevance of any reference to anorexia nervosa to support this view lacks consistency: female athletes differ in many ways from patients with anorexia nervosa, not least in their excellent physical status which is essential to deliver first-class performances.