The right arm seems a little disconnected. I'm no anatomy expert myself, but just imagine you were a ripped guy with humongous pecs. Even standing with the chest protruded, the arms rest more against the side of the chest/waist rather than pulled back as if he's ready to strike.

The way it is, he looks somewhere between preparing for a punch, and standing with his hands on his hips and elbows pointed out. Dunno if that's the look your going for, but that's just my observation. Maybe if you move his front arm around, it may make the back one easier to picture?

(Though I know it's hard to cover up that well defined abdomen ;) )