In Goju Kai how we do it, the first half of the block you inhale, and as you raise your arm, you exhale, stiffening your muscles throughout your legs, stomach neck everything for a split second (on impact in other words).

Also when you do a combo of lets say 3 strikes, inhales through the nose as you go in, exhale 3 short times through teh mouth on each strike OR a short inhale and exhale on each strike, your call, but youll need someone to force you to make this second nature (ie a sensei with a wooden sword) smile
Be the change you wish to see in the world