The “yelling” that we do in classes is referred to as a “kihap” (literally, “power yell”) and it serves two distinct â€” and very important â€” purposes:
First, the kihap is not so much the noise you make as what you do with your air. When you kihap, half of your air goes out and half is pushed down into your belly. Proper use of a kihap will give you more power by forcing the air down into the diaphragm and converting your body into a more-efficient weight-bearing mass. This is important not only in generating power for strikes, but also in helping to protect your body when taking a fall.
The second important reason we kihap is to startle an attacker or an opponent. A kihap delivered unexpectedly in a loud, sharp burst can have the effect of temporarily disorienting an attacker to give you a split second “window” to counter or deliver an attack of your own.