Stepping Therapy for Parkinson's Disease

Inclusion Criteria for Young adults and adults with normal cognition (NC): * 18 to 35 Years old * Montreal Cognitive Assessment (MoCA) score of 26 to 30 Inclusion Criteria for Older Adults: * 50 to 79 with or without MCI * 50 to 79 years old with Parkinson's disease (PD), who do NOT have impaired decision-making capacity * Participants who achieve less than 150 minutes moderate or 75 minutes vigorous aerobic activity per week (as per the US Department of Health and Human Services (HHS)), Exclusion Criteria for all groups: * Acute medical illness requiring hospitalization; * Uncontrolled congestive heart failure; * History of stroke in the past three years; * Inability to perform study procedures; * Medical or physical conditions that would preclude participation (e.g., severe arthritis or mobility problems, uncontrolled hypertension or diabetes, renal failure, history of angina with activity); * On medications that could adversely affect cognition, e.g., antipsychotics, opioids, stimulants, chemotherapy, and neurologic prescriptions to treat Multiple Sclerosis. When applicable, enrollment will be delayed until dosages are stable on e.g., Aricept, Namenda, anticholinesterase inhibitors, for at least 3 months * Psychotic disorders * Confounding neurologic conditions \[e.g., active central nervous system (CNS) opportunistic infections, seizure disorders, head injury with loss of consciousness \>30 minutes, intracranial neoplasms, stroke with neurological or neuropsychiatric sequelae\] * Substance Use Disorder, Major Depressive Disorder, and Generalized Anxiety Disorder within six months of evaluation. * Inability to provide informed consent