I had wondered about this myself, he is a very smart man. I googled searched it about 10 months ago.......let me do it again, as i want to give you accurate info. (MrsMopar's memory has a condition called Sometimers, sometimes she remembers and sometimes she doesn't

)......OK it was not real easy to find, but I found this:
"Barker has lived nearly half his life without the use of his legs, the result of a car accident during his senior year of high school. Once considered a college football prospect, Barker didn't care much about racing until the accident forced him to find another outlet for his competitive side"
He went on to get an engineering degree in mechanical engineering.