Strong Strike

Why do fighters exhale so sharply when they strike?

My friend and I have a disagreement here. I say a strong, quick breath gives your strikes a little extra power. When I lift weights, it’s a lot easier to keep going if I exhale while contracting.
My friend says that it’s to protect the body against counter shots by tightening the muscles in your core.
Who is right? Or is it a combination of both?

Just like lifting a heavy sofa or grinding through a dead lift, it tightens your abs and gives you more power. Exhaling also prevents you from getting the wind knocked out of you if you get hit.

Of course, there is also the very popular “kiai” yell to frighten your opponent into submission!

Naruto OST 1 – Strong and Strike