Gauging Effort with Kiai
The purposes of the kiai are many. Some of the instructors I’ve known say that it helps synchronize mental and physical attacks, firing the right muscles at the right time. Some say it just helps you get your energy aggression out.
Whatever the “main” purposes are, I would agree that at times it just feels right. At a particular focus point in a kata it helps punctuate a movement by kiai’ing loadly. I’ve noticed that people tend to kiai more as a class progresses and I think this is a good gauge of how focused a person or group is.
A couple weeks ago we had a class where we ended up doing heian shodan about 20 times during the whole class. We did it a few times slowly, with instruction from sensei. We went on to practice drills that had relation to the kata. We would do the kata a couple more times with more emphasis and encouragement to kiai. People would kiai louder and louder as we did it more often.
Toward the end of the class during one of our katas I couldn’t help but kiai at the last movement (normally not a kiai point in heian shodan). By this time in the class I was so intent on the kata, imagining opponents, and focusing my attacks that it just felt right to kiai at that last knife-hand strike—the “finishing blow”, as it were.
We would hope that as we get “into” a class, the frequency with which we kiai and the loudness of the kiai should increase. If we’re looking to measure effort, we’d want to remove all the provoked kiais, such as when sensei says “lunge punch, ichi … ni … san … chi, go KIAI!” This won’t tell you if the person is energized, it tells only that they listened to instructions. Also, as a class progresses I would expect more out of myself. I would expect a louder kiai, a more realistic one (e.g. unprovoked, not a primal scream).
I think its great and I would encourage everyone to avoid resisting a yell on a particular move during a kata if it makes you feel better. Kiai whenever your adrenaline is pumping so much that you can’t hold it back. I’ve experienced this and it is certainly a gauge for me.
But keep in mind that during competitions some judges may frown upon an incorrectly placed kiai [PDF].