I recently added a new form of exercise to my regimen - a recumbent trike.
This is a tricycle where you sit in a comfortable position, just like the recumbent bike machines you find in a fitness center or your home gym (but with real wheels!).
I have been an occasional biker for quite some time, but I always found a traditional bike to be uncomfortable (mostly in my neck and bottom), and since I got PD, I have also been very afraid of wiping out while riding.
Recumbent trikes are very comfortable and a lot of fun to ride, and I think they are a good choice for people with PD, since you can't easily tip over, and I suppose you can still ride one if you're balance is impaired.
The down side is they are not cheap costing between $2000 and $3000 dollars for a decent entry level trike.
P.S. The photo shows an older version of the trike I got from Trident Trikes . It is called the Trekker. It has 30 speeds, disk brakes, and a rear suspension!
tridenttrikes.com/jouta-del...
Any other recumbent triker's here?