Cocoa to Maximize Exercise Training in Older Adults - The COMET Trial

Inclusion Criteria:

* Age 55 years and older
* Slow walking speed of \< 1m/s
* Willingness to be randomized to either treatment group
* Willingness to participate in all study procedures (muscle biopsy will be optional)

Exclusion Criteria:

* Failure to provide informed consent;
* Regular consumption of flavanol and/or cocoa supplements
* Current involvement in supervised rehabilitation/exercise training program
* Absolute contraindication(s) to exercise training according to American College of Sports Medicine guidelines \[17\]
* Daytime average of systolic blood pressure ≥ 180/100mm Hg.
* Refusal to stop blood thinners such as baby aspirin dose.
* Peripheral vascular disease; peripheral neuropathy; retinopathy
* Severe cardiac disease, including NYHA Class III or IV congestive heart failure, clinically significant aortic stenosis, history of cardiac arrest, use of a cardiac defibrillator, or uncontrolled angina;
* Myocardial infarction or stroke within past year
* Significant cognitive impairment, including known dementia diagnosis or a Mini-Mental State Examination exam score \< 24
* Progressive, degenerative neurologic disease, e.g., Parkinson's Disease, multiple sclerosis;
* Severe rheumatologic or orthopedic diseases, e.g., awaiting joint replacement, active inflammatory disease;
* Severe pulmonary disease, requiring either steroid pills or injections or the use of supplemental oxygen;
* Hip fracture, hip or knee replacement, or spinal surgery within past 4 months;
* Other significant co-morbid conditions that would impair ability to participate in the exercise-based intervention
* Simultaneous participation in another interventional trial