- Volunteers will be excluded if they fail to provide informed consent, have any major comorbid disease that is uncontrolled, or any condition that is likely to limit life span and/or affect the safety of the interventions, or interfere with the conduct of the trial. Examples include: 1) unstable cardiopulmonary disease (e.g. recent MI, unstable angina, stroke within past 3 months) or unstable disease (e.g. Class IV congestive heart failure: 2) severe orthopedic (e.g. awaiting joint replacement) and/or neuromuscular (e.g. multiple sclerosis, amyotrophic lateral sclerosis, active rheumatoid arthritis), 3) significant cognitive impairment, defined as a known diagnosis of dementia or positive screening test for dementia using the Mini-Mental State exam (i.e. MMSE score <24),43 4) cancer requiring treatment in the past 5 years, 5) documented history of pulmonary embolism in the past 6 months, 6) positive exercise stress test for cardiac ischemia, and 7) HbA1c >11%.