Save the shirt, save the long countdown (for heavens' sake learn how to take a real punch then ask for a real punch) and get back to work. Unless you only want to impress your dog or parrot, those muscles won't just grow on their own.
So many battles could be spared if two or more muscled men (or fit women) simply got together to test their arm strength against each other. A power challenge, usually one-on-one, where you get one winner and one loser. So, where will you stand? Arm wrestling is the name of the game. It's not just muscle though, Einstein, it's also technique and mind-focusing. Keep yourself together when you see your arm failing you, keep your cockyness down when victory smiles at you, as both arms swing, hands against each other, same direction, same purpose: to assert dominance over your opponent.