Effects of Physical and Psychosocial Stress on Functional Hypothalamic Amenorrhea in Exercising Women

Inclusion Criteria: * participates in structured running or cycling exercise for at least 30 minutes on 4 days per week or more * have regular periods every 21 to 35 days * have not used hormonal contraceptives for at least the past 6 months * are not currently or trying to become pregnant or are breastfeeding, and have not been pregnant or breastfeeding for the past 12 months * have never been diagnosed with a menstrual cycle disorder (e.g., menorrhagia, amenorrhea, dysmenorrhea, polycystic ovary syndrome \[PCOS\], endometriosis, premenstrual dysphoric disorder \[PMDD\], menstrual migraines, ovarian cancer, ovarian insufficiency, uterine or endometrial cancer) * have never been diagnosed with a metabolic disease (e.g., hypothyroidism, hyperthyroidism, Cushing disease, Addison's disease, diabetes) Exclusion Criteria: * missing \> 4 consecutive days of aerobic exercise (i.e., running, cycling, cross training) if assigned to the exercise intervention groups * they indicate they "Could not participate at all due to a health problem" or have had to modify their exercise training, felt their injury, illness, or other health problem has affected their exercise performance, or experienced symptoms/ health complaints greater than "To a minor extent" on the Oslo Sports Trauma Research Center Questionnaire (exercise training intervention group) * demonstrate clinical low energy availability as defined as energy availability \<30 Kcal/kg fat free mass in the first two months of at-home monitoring * report menstrual cycle lengths \<21 days or \>35 days in the first two months of at-home monitoring * do not demonstrate an anticipated rise in progesterone levels during the latter half of their cycle and luteinizing hormone levels at mid-cycle compared to tests taken during the first few days after menses in the first two months of at-home monitoring * begin taking a hormonal contraceptive * become pregnant * are diagnosed with a menstrual cycle disorder (e.g., menorrhagia, amenorrhea, dysmenorrhea, polycystic ovary syndrome \[PCOS\], endometriosis, premenstrual dysphoric disorder \[PMDD\], menstrual migraines, ovarian cancer, ovarian insufficiency, uterine or endometrial cancer) * are diagnosed with a metabolic disease (e.g., hypothyroidism, hyperthyroidism, Cushing disease, Addison's disease, diabetes), 10) are diagnosed with a major cardiovascular disease, respiratory disease, or musculoskeletal injury * are unable to follow instructions for any of the procedures