"When I was first diagnosed, I felt like I was on an icy slope with no axe to arrest the progression of the disease. Through a series of happy coincidences, I learned about the work of neuroscientist Jay Alberts at the Cleveland Clinic , pedalingforparkinsons.org. I began cycling at 80-90 rpms 4-5 times/week for at least an hour, generally 1.5-4 hours. Within less than a month nearly all of my symptoms disappeared, so much so that my doctor told me that if he didn't know I had PD, he wouldn't know. I still take 6 mg of ReQuip XL (down from 8) and 1 mg of Azilect, but the changes happened when I started the forced pace cycling. It is MOST important to pedal at 80-90 rpms. We don't know why, but it is working for me."

The above quote implies that VE AT 80 to 90 rpm does the trick while controlled research claims that only FE is useful. The research paper is confusing because it doesn't say if the wpd achieves same high speed as that in FE, why he does not get same benifits?
FE requires double seat and a strong partner, both difficult to have.
I have been stationary cycling twice daily for 15 mins at 85 rpm which is my "killing" limit.
I am sure it has helped my general health perhaps even my pd. It aso resolved my knee joints pain,
Imad