Moderate Versus High Volume Light-Moderate Intensity Exercise for People With Moderate Parkinson's Disease

Inclusion Criteria: Participants recruited for this study will be age 40 and older with diagnosis of "definite" PD based upon established criteria (Hughes, Daniel et al. 1992) and determined by a board-certified neurologist with specialty training in movement disorders. Individuals must have presented with asymmetric symptoms that included at least 3 of the cardinal signs of PD (rigidity, bradykinesia, tremor, postural instability), and must show clear symptomatic benefit (e.g., alleviated rigidity, bradykinesia, and tremor) from antiparkinsonian medications, e.g., levodopa (Kempster, Williams et al. 2007). They should be in H\&Y stages 2, 2.5 and 3, and receive a Montreal Cognitive Assessment (MoCA) score \>17 (Litvan, Goldman et al. 2012). Age 40 is the upper limit for young onset PD. The investigators will not recruit individuals with a history of significant alcohol or drug use, nor habitual users of antipsychotics. The investigators will observe patients while OFF their antiparkinsonian medications to avoid dyskinesia, and medication fluctuations that may impact neurophysiology and motor examination. The investigators have successfully observed patients while OFF in several previous trials. The following inclusion criteria apply: * MoCA score \>17 * Able to walk with or without an assistive device at least 10 feet * Best corrected/aided acuity better than 20/70 in the better eye * Willingness to be randomized to a treatment group * H\&Y stages 2, 2.5 and 3 * Show clear symptomatic benefit (e.g., alleviated rigidity, bradykinesia, and tremor) from antiparkinsonian medications * Fluent in English to be able to comprehend and participate; older than 40 years; Diagnosis of definite Parkinson's disease by board certified Movement Disorders Neurologist, using standardized UK Brain Bank criteria Exclusion Criteria: Participants recruited for this study will be age 40 and older with diagnosis of "definite" PD based upon established criteria (Hughes, Daniel et al. 1992) and determined by a board-certified neurologist with specialty training in movement disorders. Individuals must have presented with asymmetric symptoms that included at least 3 of the cardinal signs of PD (rigidity, bradykinesia, tremor, postural instability), and must show clear symptomatic benefit (e.g., alleviated rigidity, bradykinesia, and tremor) from antiparkinsonian medications, e.g., levodopa (Kempster, Williams et al. 2007). They should be in H\&Y stages 2, 2.5 and 3, and receive a Montreal Cognitive Assessment (MoCA) score \>17 (Litvan, Goldman et al. 2012). Age 40 is the upper limit for young onset PD. The investigators will not recruit individuals with a history of significant alcohol or drug use, nor habitual users of antipsychotics. The following exclusion criteria apply: * Untreated Major Depression and major psychiatric illness * History of stroke, or traumatic brain injury * Pure-tone threshold average sensitivity at 0.5, 1.0,and 2.0 kHz exceeds 40 dB * Alcohol abuse and/or use of antipsychotics * Planning to leave the area for \>1 month during the study time period. * Taking moderate to high doses of beta-blockers with a resting heart rate below 60 beats/min given that exercise intensity is measured through target heart rate. * 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 * Other significant co-morbid disease that would impair ability to participate in the exercise-based intervention, e.g. renal failure on hemodialysis, excessive alcohol use (\>14 drinks per wk)