The goal of this clinical trial is to learn whether training with blood flow restriction (BFR), combined with aerobic exercise (performing stepping on a Nu-Step exercise machine), can help improve mobility and other outcomes in people with progressed Parkinson's disease. The investigators hypothesize that training with BFR and aerobic exercise will produce enhanced outcomes related to mobility and quality of life. BFR uses inflatable cuffs placed on participants' upper legs to gently reduce blood flow to the legs while exercising. This has been shown in studies in older adults and Parkinson's disease to improve strength while training with lighter loads, which may be helpful for people with Parkinson's. Participants will be asked to complete 2 weekly training sessions (approximately 30 minutes each) for 8 weeks consisting of supervised aerobic stepping exercise on a Nu-step machine with BFR application during timed intervals. In addition to the training sessions, participants will be asked to periodically perform confidential surveys and tests related to function and disease symptoms, and wear a provided smartwatch (which can be kept upon successful completion of the study). All sessions involve individual monitoring and medical supervision by licensed physical therapists as well as access to all necessary equipment.