Examining the Role of Female Endogenous Sex Hormones in Eccentric Exercise

Inclusion Criteria: * 18-35 years of age * BMI of 18.5-29.9 as a BMI below or above these cut points results in highly varied menstrual cycle lengths \[15\] * Not taking contraception or other types of medication that could influence reproductive status * Regular menstruation * Non-pregnant * Medically free from chronic diseases * Novel to downhill running * Weight greater than or equal to 110 lbs * Not taking exogenous hormones * Not suffering from known gynecological disease (i.e., PCOS, endometriosis, etc.) that may influence menstrual cycle regularity Exclusion Criteria: * Amenorrhea or oligomenorrhea * Perimenopausal or menopausal * Recreational or professional trail or downhill runner * On a form of contraception * Cardiac disability * Pacemaker * Arterial disease * Uncontrolled hemorrhage * Blood clots * Pregnant or trying to become pregnant * Cancerous lesions * Sensory or mental impairment * Unstable fractures * Weight less than 110 lbs * Suffering from gynecological disease (i.e., PCOS, endometriosis, etc.) that may influence menstrual cycle regularity * Taking exogenous hormones