Shortly after diagnoses I chose high-cadence cycling as my main form of exercise to combat progression of the disease. I bought a stationary exercise bicycle and exercised for about one hour per session (including warm-up and cool-down).
After a few months I found that, soon after starting a session, my right foot would cramp up and turn inwards, in a claw-like fashion. Once this occurred, I would stop cycling and rotate the foot in the air for a minute or two until the cramping disappeared. I could then resume cycling for a few minutes until the cramping returned. It would usually be about fifteen to twenty minutes into the session before the cramping stopped happening.
A couple of years ago I decided to add arm-cycling to my exercise session, and bought a small stationary exercise bike for this purpose. This bike has no seat, its pedals are suited to hand use, and I have it sitting on a small desk. The plan was to keep the exercise session at one-hour duration (30 minutes arm-cycling followed by 30 minutes leg-cycling).
Now for the punch line!
As soon as I changed over to the new session format, the cramping in my right foot stopped happening. I've also tried shorter arm-cycling sessions and seen that even an arm-cycling session of 10 minutes duration is sufficient to prevent cramping during the leg-cycling session. I do my exercise session first thing in the morning, straight after my medication.