Hi, jaki --
Cycling has been shown to be highly beneficial to Parkinson's patients. If you can do it and enjoy it, by all means use that as one of your forms of exercise. Personally, at the gym I find the elliptical more energising and effective for flexibility in my joints than the cycles. Nevertheless, I still use the recumbent cycle once in a while. We pwp need vigorous exercise as long as our balance allows. Yet Saturn's Pilates, like yoga and Tai Chi, is also a needed form of exercise: a gentler exercise promoting stretching, flexibility, balance, and smooth movement. The main thing is simply to keep moving!
Best regards, J