Countermeasures to Circadian Misalignment

Inclusion Criteria: 1. 18-35 old; men and women; equal numbers of women and men will be included. 2. Body Mass Index (BMI) between 20.0 and 24.9 ("normal" weight). 3. Physical activity history: inactive to habitual moderate physical activity level 4. Sleep/wake history: habitual sleep duration between 7-9.25 hours. 5. Altitude history: Potential subjects must have lived at Denver altitude or higher for at least 3 months prior to inpatient stay. Exclusion Criteria: 1. Any clinically significant medical, psychiatric, or sleep disorder 2. Use of prescribed medications/supplements/illicit drugs within one month prior to study 3. History of shift work in year prior to study, or travel more than one time zone in three weeks prior to study. \[NOTE: Subjects can be studied at a later date.\] 4. Women with history of prior gynecological pathology, \<1 year post-partum, breast-feeding and/or pregnant. 5. Non-English speakers will be excluded, as we do not have access to a translator who could rely accurate information to the participant for the consent or throughout the study.