Immune Cells During Disuse and Recovery

Inclusion Criteria: 1. Age between 18-35 and 60-85 yrs 2. Ability to sign informed consent 3. Free-living, prior to admission Exclusion Criteria: * History of cardiovascular disease (e.g., CHF, CAD, right-to-left shunt) * History of endocrine or metabolic disease such as hypo/hyperthyroidism and diabetes * History of kidney disease or failure * Vascular disease * Risk of DVT including family history of thrombophilia, DVT, pulmonary emboli, myeloproliferative diseases including polycythemia (Hb\>18 g/dL) or thrombocytosis (platelets\>400x103/mL), and connective tissue diseases (positive lupus anticoagulant), hyperhomocystinemia, deficiencies of factor V Leiden, proteins S and C, and antithrombine III * Use of anticoagulant therapy (e.g., Coumadin, heparin) * Elevated systolic pressure \>150 or a diastolic blood pressure \> 100 * Implanted electronic devices (e.g., pacemakers, electronic infusion pumps, stimulators) * Cancer or history of successfully treated cancer (less than 1 year) other than basal cell carcinoma * Currently on a weight-loss diet * Chronic systemic corticosteroid use (≥ 2 weeks) within 4 weeks of enrollment and for study duration (intra-articular/topical/inhaled therapeutic or physiologic doses of corticosteroids are permitted) * Androgens or growth hormone within 6 months of enrollment and for study duration (topical physiologic androgen replacement is permitted) * History of stroke with motor disability * A recent history (\<12 months) of GI bleed * History of liver disease * History of respiratory disease (acute upper respiratory infection, history of chronic lung disease) * Pregnancy as determined by a pregnancy test * Any staff members who report directly to an investigator or who report to someone who reports directly to an investigator. * Any other condition or event considered exclusionary by the PI and faculty physician