"Cycling on stationary bikes may provide symptomatic relief for people with Parkinson’s disease, especially if they cycle using what’s described as Forced Exercise, i.e. pedaling at a rate faster than their voluntary cadence. " Parkinson's Cycling Coach website says.
I personally do this 3 times a week with a group of people with No PD and that really helped me a lot.
Please share your ideas, experience about indoor group cycling for PD.