He's super fit and has so much core strength, if he doesn't have problems I probably wouldn't worry too much about it. If you can't get him to slow down enough to warm him up in front of the bike, then just walk him around the block a couple of times before you head out.
I'm not a big fan of stretching muscles before exercise, but right after a run I always do some massage and some kind of... oh, vigorous scratching, I guess, of their thighs and lower backs, and some gentle hip and shoulder extension stretches both straight back and, in the back, with the hip slightly abducted (to the side, like a dog lifting his leg to pee). Then do a couple of front-feet-on-the-perch stretches when we get home.