The Effect of Mixed Exercise and Metabolic Stress in Relationship to Age in Healthy Men

Inclusion Criteria: * Community dwelling, healthy men age 18 to 80 * Body-Mass Index (BMI) 18-30 kg/m2 * Willingness to provide written informed consent * Physician acceptable screening ECG for participants 60 years and older Exclusion Criteria: * recent use of psychotropic or neuroactive drugs (within five biological half-live) * obesity (outside weight range above) * acute weight change (loss or gain of \>2 kg in 6 weeks * Laboratory test results not deemed physician acceptable * triglycerides \> 300 * BUN \>30 * creatinine \> 1.5 mg/dL * liver functions tests twice upper limit of normal * electrolyte abnormality * anemia; hemoglobin \< 12.0 gm/dL * drug or alcohol abuse * psychosis, depression, mania or severe anxiety * acute or chronic organ-system disease * endocrinopathy, other than primary thyroidal failure receiving replacement * untreated osteoporosis * nightshift work or recent transmeridian travel (exceeding 3 time zones within 7 days of admission) * PSA \> 4.0 ng/mL, History or suspicion of prostatic disease (elevated PSA,indeterminate nodule or mass, obstructive uropathy) * History of carcinoma (excluding localized basal cell carcinoma removed or surgically treated with no recurrence * History of thrombotic arterial disease (stroke, TIA, MI, angina) or deep vein thrombophlebitis * History of CHF, cardiac arrhythmias, congential QT prolongation, and medications used to treat cardiac arrhythmias * Gynecomastia \> 2 cm, untreated * Untreated gallbladder disease * History of smoking greater than one ppd.