Well for triceps during 5x5 I had bench (of course) but I also did Dips on Fridays. My triceps have actually developed fairly nicely as well, my weakest point isn't the lockout as much as the initial push, I'll get stuck as soon as I'm pushing it off my chest but with a little bump I've got it for the rest of the rep. So it's definately my chest that needs to be strengthened, by arms, I meant mostly my biceps.