Influences of Long-acting Reversible Contraceptives on Iron Status and Physiological Responses to Extreme Environments in Women

Inclusion Criteria: * • Females, age 18-40 y * Females taking monophasic oral contraceptives or utilizing implantable contraception (intrauterine device, implantable bar) for at least one year, and be at least one year removed from the removal end point (e.g. before year 4 for a 5-year IUD) * In good health as determined by OMSO (Office of Medical Support and Oversight) * Passed most recent Army Combat Fitness Test (ACFT) (military volunteers only) or exercise at least 2 times per week (civilian volunteers) * Willing to not drink alcoholic beverages for 24 hours before each testing session * Willing to not consume caffeine 12 hours prior to any testing sessions * Willing to refrain from any exercise and additional moderate to strenuous physical activity 24 hours prior to testing * Willing to stay and exercise in an altitude chamber (the size of a dorm room) for \~6 hours * Supervisor approval for federal civilian employees and non-HRV active-duty military personnel stationed at NSSC. Exclusion Criteria: * • Females who are pregnant, planning to become pregnant during the study, or breastfeeding. * Taking prescription, over the counter medication, or dietary supplements, other than a contraceptive (unless approved by OMSO and Principal Investigator (PI)) * Tobacco or nicotine users, or anyone who has used tobacco or nicotine within the last four months * Physical problems/injuries (e.g., current stress fractures, musculoskeletal strains) that would affect walking or running on a treadmill * Allergy to skin adhesive * Heart, lung, kidney, muscle, endocrine, or nerve disorder(s) as determined by OMSO * History of heat intolerance or orthostatic intolerance * Diagnosed and/or treated for fluid/electrolyte imbalance within the last 30 days * History of obstructive disease of the gastrointestinal tract including (but not limited to) diverticulosis, diverticulitis and inflammatory bowel disease, peptic ulcer disease, Crohn's disease, ulcerative colitis. * Scheduled MRI within 2 weeks after completing a heat or cold test * Actively dieting with the intent to lose weight * History of cold injuries of any severity (e.g., frostbite, trench foot, chilblains). * Raynaud's syndrome * Cold-induced asthma/bronchospasm * Not willing to have small areas of skin on the body shaved (if deemed necessary for attachment of study instrumentation) * Born at altitudes greater than 2,100 m (7,000 ft) (e.g., Mexico City, Mexico) * Living in areas that are more than 1,200 m (4,000 ft) (e.g., Colorado Springs, CO) or have traveled to areas that are more than 1,200 m for five days or more within the last 2 months * Prior diagnosis of High Altitude Pulmonary Edema (HAPE) or High Altitude Cerebral Edema (HACE) * Abnormal blood count in accordance with OMSO - Normal Hb women: 11.1-15.9 g·dL-1 or Normal Hct women: 34.0-48%, or presence of abnormal blood chemicals (hemoglobin S or Sickle Cell Trait) * History of pneumothorax * History of hypertension * Blood donation within 8 weeks of beginning the study * Any recent (within 4-6 weeks) and or expected history of prolonged periods of immobility or limited activity (including recent or upcoming surgery) * Evidence of apnea or sleeping disorder (narcolepsy, insomnia, etc.)