I'm going to do this once I get a treadmill lol. I would start out by just keeping Max on the treadmill while it's off and pet him and praise him for a few days while on it. Then, I would tie him up to it while it's on VERY low, so he's not startled, and so he will only have to walk slowly. As he gets more advanced, then I would turn it up to a run, and he wouldn't have to be tied to it