For the first time, this project will define the impact of high volume (HV) exercise compared to moderate volume (MV) exercise for Veterans with moderate PD (Stages 2-3). Volume of aerobic exercise (AE) has not been previously well studied in PD, in moderate PD, nor in Veterans. Exercise is now prescribed as a first line therapy in PD. Exact combinations of frequency, duration (the product of which is volume) and intensity of AE need to be determined for optimal delivery of exercise for PD. In contrast to studies of high intensity exercise, which is being investigated in a major stage 3 clinical trial, SPARX3, few studies have examined the impact of volume, in particular HV in PD. As such, AE volume is primed for evaluation, for its effects on gait measures, and overall physical activity (PA). Like (SPARX3), evaluation of volume must include clinically-relevant behavioral measures, e.g., gait parameters, and disease severity; biomarkers of neurodegeneration, representing inflammatory, and neurotrophic mechanisms. Given the strong impact of PD on autonomic and sympathetic processes in PD (Sabino-Carvalho et al., 2020) cardiovascular and vascular processes should also be evaluated- particularly in moderate PD who have OFF-time and greater motor dysfunction. The investigators' published work shows HV light-moderate intensity Partnered dance AE (PDAE) (5 days/week, for 2-3 weeks) - improved gait, motor function and neuromuscular control in people with moderate PD. These functional changes were comparable to changes seen in programs of longer duration and lower weekly volume. PDAE has been tailored for Veterans with PD since 2011 and is adaptable for MV or HV. This project explores effects of exercise dosing that make good use of patients' high functioning times and will lead to enhance gait parameters and more PA. The primary outcome measure is preferred gait cadence, a clinically relevant variable for gait training studies, and which the data show is strongly associated with PA. At the Atlanta VA, for 13 years, Dr. Hackney (PI) and her team have developed a research infrastructure to investigate rehab treatments for Veterans with PD -most of whom have moderate stage PD. The expertise, resources and infrastructure the team has accumulated are crucial for the proposed work. This RCT assigns n=102 (34 per group) older Veterans with PD to 52 weeks of PDAE at HV or moderate volume (MV) or to a MV control (MVWALK). Overall exercise dose will be 112.5 hours over 52 weeks. MV-PDAE and MV-WALK classes will meet twice-weekly for 65-minutes. HV PDAE classes will meet 5 times a week for 90 minutes for three weeks at trial onset followed by one HV week every 4 weeks for a year. Gait cadence will be measured with inertial sensors. PA will be measured with accelerometry and a questionnaire. Outcomes will be assessed at baseline (before intervention), and at 52 weeks (intervention end). The investigators assume 20% attrition and will recruit 21 additional participants, totaling 123 Veteran participants (41 per group). Aim 1 will compare the impact of AE volume on gait cadence and PA. Aim 2 will compare the impact of AE volume on blood biomarkers: IL-7, BDNF and CRP. Aim 3 will compare the impact of exercise volume on vascular function and aerobic capacity