I personally think for the running animation, he should hold the hammer almost parallel(spelling?) with his shoulders, and really make it look like he has a hard time hauling it around. I think this concept would work really well when it comes time to make the swinging animation, like he has to put all his strength into it. That's just my thoughts anyway, the animation atm isn't bad, just a little effortless to my eye. Also, on the frame where the hammer head is half covered by his body, the handle looks a little bit mangled.