I can not begin to explain how much work he's done to be able to do this. I could start by showing you pictures of physical therapy with his feet literally strapped to the pedals of a trike. Or show you video of him attempting to steer that trike will also attempting to pedal.
You see, riding a bike is a very complicated maneuver.
This statement was a complete surprise to me and - had someone attempted to tell me that before meeting my son- I would've scoffed and walked away from the clearly insane person. But given that it requires alternating movements on either side of the body to Pedal (one foot up, one foot down. one arm forward, one arm back)- also for steering and then an upper body control (steering) and a lower body control (pedaling)- it can be a lot for someone figuring out how to use this body of his.
I'm thrilled and over the moon for him. As is typical he wants to ride all the time so he can master this new accomplishment.