Nothing seems to tire out my 4 month puppy like a 20 minute walk since it's mentally and physically stimulating. The problem is the first few times he walked by my side, but now he's pulling ahead excitedly. So I've started loose leash training. Problem is I can walk about half a block before he gets overstimulated and starts pulling and pulling no matter how many times I stop or turn around. I think i have to stop and say "uh uh" about 70 times a half block walk. So how do i get him this kind of exercise without undoing the loose leash work by letting him pull. Fetch doesn't seem to tire him out and I don't have a fenced in back yard.