Hmmm hardened skin and bones, first off, to keep the use of his power from tearing himself apart. Main powers would be that he has extremely powerful muscles that, if pulled back, can snap forward with enough power to.... well, I guess the amount of power involved would depend on how far along his training with it is, but enough to break through a steel-reinforced concrete wall would not be out of the picture, as well as with enough speed as to cause a vacuum backlash that would shoot in the opposite direction.