I presented on the topics you referenced at the FDA headquarters in a patient-focused panel discussion on Sept. 22, 2015. You can find a written copy of the presentation at http://parkies.org/FDA/FDApattersonSummary1.2.pdf . I am working on an expansion of this that I hope to publish at some point.

Like you I am frustrated with the lack of information on this topic. In particular I have not found ANY long term studies of high cadence aerobic exercises on human PD patients.

So I am doing my own amateur one. Hopefully it can be useful to an academic researcher who wants to see some possible directions. At this point I've been cycling for nearly seven years generally daily, keeping exercise session level information for the last 3 years, and detail input from wearable sensors for the last 1 year. At some point I hope to make some of this information available.

As far as cramps are concerned, I'd refer you to the work of Dr. Arnie Baker (Arnie Baker Cycling) who identifies elemental nutrients helpful for avoiding cramps: sodium (which we probably get more than enough of), potassium, magnesium, and calcium. See your dietitian for dosage suggestions.

I like upright bikes. If you have discomfort or pain when riding, take a video clip of your riding and show it to your physical therapist. Mine gave me useful suggestions.

Bill Patterson