Treadmill Exercise Prescriptions to Improve Fitness Versus Ambulatory Function After Stroke.

Inclusion Criteria: 1. Ischemic stroke greater than or equal to 6 months prior in men or women ages 40- 85 yrs. Hemorrhagic stroke greater than or equal to one year prior in men or women ages 40-85 years. 2. Residual hemiparetic gait deficits. 3. Already completed all conventional inpatient and outpatient physical therapy. 4. Adequate language and neurocognitive function to participate in exercise testing and training (specific screening instruments used.) Exclusion Criteria: 1. Already performing aerobic exercise 3 X / week. 2. Increased alcohol consumption. 3. Cardiac history of: * unstable angina, * recent (less than 3 months) myocardial infarction, congestive heart failure (NYHA category II-IV); * hemodynamically significant valvular dysfunction. 4. Medical History: * recent hospitalization (less than 3 months) for severe medical disease, * PAOD with claudication, * orthopedic or chronic pain condition restricting exercise, pulmonary or renal failure, * active cancer, * untreated poorly controlled hypertension measured on at least 2 occasions ( greater than160/100) or diabetes mellitus (fasting glucose greater than 180 mg/dl, HgA1C greater than 10%) unable to be controlled medically within 3 months; g) Anemia defined by hematocrit less than 30 . (5) Neurological history of * dementia with Mini-Mental Status Score less than 23 (less than 17 if education level at or below 8th grade), and diagnostic confirmation by neurologist or psychiatrist, * severe receptive or global aphasia which confounds testing and training, operationally defined as unable to follow 2 point commands, * hemiparetic gait from a prior stroke preceding the index stroke defining eligibility, * non-stroke neuromuscular disorder restricting exercise (e.g. Parkinson's Syndrome), * untreated major depression. (6) BMI \> 40. Special fMRI Exclusion Criteria: 1. Metallic implants above the waist, except sternal wire implants. 2. Any type of implanted stimulator(cardiac, spinal, bladder, auditory 3. Claustrophobia 4. Pregnancy- A negative urine pregnancy test will be required prior to undergoing fMRI for women of child- bearing potential.