A document detailing the design of the CYCLE II study has recently appeared.

Effectiveness of a Long-Term, Home-Based Aerobic Exercise Intervention on Slowing the Progression of Parkinson Disease: Design of the Cyclical Lower Extremity Exercise for Parkinson Disease II (CYCLE-II) Study:

Effectiveness of a Long-Term, Home-Based Aerobic Exercise Intervention on Slowing the Progression of Parkinson Disease: Design of the Cyclical Lower Extremity Exercise for Parkinson Disease II (CYCLE-II) Study | Physical Therapy | Oxford Academic

(Abstract only - the rest is behind a paywall)

Also of interest (maybe) is a recently released report on a Cleveland Clinic study involving the Pedaling for Parkinson's program.

Individuals With Parkinson Disease Are Adherent to a High-Intensity Community-Based Cycling Exercise Program:

Individuals With Parkinson Disease Are Adherent to a High-Intensity Community-Based Cycling Exercise Program - PubMed

(Abstract only - the rest is behind a paywall)

There is also a Supplementary Video where one of the researchers talks for about 3 minutes while standing beside a Peloton bike.