Here are some helpful links:

• National Institute of Neurological Disorders and Stroke
• Parkinson's and Parkinson's Syndrome
• Alzheimer's Disease
• American Heart Association
• American Physical Therapy Association
• American College of Sports Medicine
• American Medical Association
• National Institute on Aging
• Centers for Medicare & Medicaid Services
• WebMD
• American Senior Fitness Association
• MEDLINEplus