This chapter focuses on explaining the interaction between the hypothalamic–pituitary–ovarian axis, menstrual and oral contraceptive cycles with exercise. The intent herein is to give the basic physiology and endocrinology framework that allows the reader to understand the dynamic hormonal changes that occur within women as related to their reproductive systems in turn to also provide a contextual basis for the role of exercise to impact on the hormonal components of the female reproductive system. In so doing the goal is to prepare the reader for some of the in-depth discussions on female physiology-endocrinology and exercise in the subsequent chapters of this book.