Parkinson's disease experts agree that exercise is beneficial for PD patients at most stages. The benefit of exercise is supported by an ever-expanding body of research, indicating positive effects on many aspects of daily living and performance. There is a growing body of research pointing towards vigorous exercise, with careful consideration of patient safety, as a potentially being neuroprotective.
Ridgel AL, Vitek JL, Alberts JL. Forced, not voluntary, exercise improves motor function in Parkinson's disease patients. Neurorehabil Neural Repair. 2009;23(6):600-608.