Abstract
Exercise training can have an impact on the menstrual cycle. If the exercise load is great enough it can lead to irregular or even the complete absence of menses, which has implications for reproductive health. Conversely, the menstrual cycle can affect exercise performance. Disruptions in hormonal balance throughout the menstrual cycle have been implicated in altered muscular strength, exercise endurance capacity, body temperature, metabolism and blood flow. There is also growing evidence for a link between female sex hormones and health, including a relationship between melatonin, menstrual dysfunction and breast cancer. The mechanisms for and consequences of these relations are yet to be elucidated.