Metformin may shield aging muscles from inactivity

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Age 60y and older * Ability to sign informed consent * Free-living, prior to admission Exclusion Criteria: * Personal history of cardiovascular disease * Uncontrolled endocrine or metabolic disease (e.g., hypo/hyperthyroidism, HbA1c ≥6.5%) * Evidence of kidney disease or failure (defined as serum creatinine \> 1.5mg/dL) * Vascular disease or risk factors of peripheral atherosclerosis. (e.g., uncontrolled hypertension, obesity, diabetes) * Risk of Deep vein thrombosis including family history of thrombophilia, Deep vein thrombosis, pulmonary emboli, myeloproliferative diseases including polycythemia (Hb\>18 g/dL) or thrombocytosis (platelets\>400x103/mL) * Use of anticoagulant therapy (e.g., Coumadin, heparin) * Uncontrolled hypertension (e.g. systolic pressure \>160 or a diastolic blood pressure \> 100) * Cancer or history of successfully treated cancer (less than 1 year) other than basal cell carcinoma * Currently on a weight-loss diet or body mass index \> 30 kg/m2 * Inability to abstain from smoking for duration of study * HIV or hepatitis B or C\* * Subjects excluded due to positive screening results, including HIV, hepatitis B or hepatitis C, will be immediately scheduled for counseling and follow-up testing as needed, and will be advised to consult their primary physician. * 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) * Subjects with hemoglobin or hematocrit lower than accepted lab values * History of stroke with motor disability * A recent history (\<12 months) of GI bleed * Depression \[\>5 on the 15 items Geriatric Depression Scale (GDS)\]\* \*This criteria will only apply to subjects in the bed rest arm. * Liver disease (the ratio of serum aspartate aminotransferase to serum alanine aminotransferase 2 times above the normal limit, hyperbilirubinemia) History of respiratory disease * Currently taking estrogen products (topical vaginal products are not exclusionary (e.g. cream)) * Recent travel history as defined by 4 hours of travel by airplane in the last week * Any other condition or event considered exclusionary by the PI and faculty physician