immune cells during disuse and recovery

Conditions: Muscle Disuse

Summary: this is an interventional study enrolling healthy individuals aged 18-35 and 60-85 to understand the recovery of muscle health following a period of inactivity. the enrollment goal is 45 participants. the study will occur over the course of 1-2 months where participants will undergo testing before and after a 2-week limb immobilization period.

visit 1 (pre-testing)- after signing a consent form, participants will undergo a blood screening and an oral glucose tolerance test. after the visit, participants will be provided with a step activity monitor to track their level of activity. a dietary assessment will also be determined. visit 2- at a later time, the participant will return to the research center for a biopsy, blood draw, body composition scan, mri and muscle strength testing. 2-week leg immobilization period- after visit 2 , the participant will return home and undergo a 14-day leg immobilization period using the equipment and instructions provided at visit 2. visit 3- during the limb immobilization period, participant will return to the research center for a single blood draw. visit 4- at the end of the 2-week limb immobilization period, the participant will return to the research center to undergo another biopsy, blood draw, body composition scan, mri and muscle strength testing. visit 5- 2 days after the 2-week limb immobilization period, the participant will return for a biopsy and blood draw. visit 6- 7 days after the 2-week limb immobilization period, the participant will be asked to return for a final biopsy, blood draw, body composition scan, mri and muscle strength testing.

Eligibility criteria:
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