This is a thread i ripped from the Uechi-ryu message forum, i thought you might like it. I dont take any credit and i’m not exactly promoting Kiai’s, but just giving some reasons for it. It’s not mindless screaming except maybe when done by a five year old Blackbelt 
---------------ENJOY
There is a strong belief that exhalation facilitates the concentration of physical output . Also , I read that nature says the maximum concentration of physical output is achieved on the exhale !
If our system is founded on animals [ tiger] ; witness the fact that tigers roar when they charge . They must exhale to roar ; they achieve physical output on the exhale ! Why was this most important aspect of animal behavior disregarded in manufacturing Uechi Ryu ??
< Battle cries are common to human combat as well . Battle cries can only be made on the exhale . Also , if the noise is intense and explosive enough , it has the effect of paralyzing the opponent for a fraction of a second gaining an advantage ! In street fighting the combination of the loud ‘bark’ and the attack has the paralyzing effect >
The kiai in combat also has the " Psyching up " effect needed to engender a sense of control and resultant manageable heart rate of between 115 and 145 beats per minute !
The kiai has many manifestations , doesn’t have to be loud in the kata if not desired , but it can be there very subtly , ’ cooking in the oven’ for full release when you need it most !
Van Canna
Amongst other things, the kiai is good for beginners of hard styles because it reminds them/forces them to breathe at well-defined intervals in kata (people often forget to breathe while doing kata, right?) which are more rigorous and physically more demanding
moulton
Re: KIAI!!!
The kiai (“spirit shout” or “spirit yell” for lurkers who are wondering) has a few purposes:
- get the air out of the body, so that on an opponents counter-attack it (your wind) can’t be knocked out of you.
- frighten the opponent. A little story. I did a demonstration a few months ago breaking some concrete slabs, the front row of the audience was 40’ from the stage. The last row was 120-140’(?) away. When I kiaied and broke the concrete in two I heard people jump and chairs rattle throughout the audience. There is no doubt … the kiai can be very frightening.
- forces you to breath. Very important.
- forces you to tighten. This momentary tightening of the body causes the extra explosion of power. How, I don’t know the body mechanics well enough, but it seems to work (maybe the kiai is a placebo itself … I think that if I kiai I will hit harder and so I do?)
- Energy flow(?). I have been told that from an energy flow perspective this forces energy out from the center of your body (where it is abundant) out to the extremties where it is less abundant. Perhaps a funkier way of saying #4 above.
- Energy projection(?). Even more mystical the kiai forces the energy out of your body by spiritual means into the body of the opponent causing damage. Again, another explanation I have heard over the years.
vs.
The short breath. I like the short breath, I use it in all my kata, when I am not doing a kiai (I believe the kiai should be reserved for final blows in a kata). I also use the short breath when doing technique, doing a kiai often is too exhausting, and perhaps defeats the purpose (i.e. I want to do the kiai when I want to really do some damage, like at the end of a combination of blows … so it sounds like ssss, ssss, KIAI)!. But anyway, the purpose seemingly of the short breath is like the kiai but less intense.
- Forces you to breath. Very important!
- Forces you to tighten a little. More power.
- Gets most of the air out of you so that it won’t be knocked out of you. I think I read somewhere that the short breath gets something like 75% of the air out?
These are my observations of the kiai and short breath. There is a time and place for each. I don’t think that sanchin kata, for example, has a kiai step … and in fact the purpose of that kata (body tightening and conditioning and such) it makes more sense to keep your energy. Or at least the way we do so sanchin kata.
Osu!
Jason
I couldn’t have said it better. My biggest problem in coming to Uechi-ryu after all these years of Shotokan and similar arts is the lack of kiai. Except in Sanshin… there is no point in that kata that lends itself to kiai. In the first dojo wherein I trained, we did a different version of Sanchin, but there was no kiai there, either.
Another use of kiai is as a defensive technique. After years of sparring with fairly heavy contact to the body (browns belt and higher), kiai-ing as a punch or kick hits you is very effective. It only works when it is done reflexively.
Kiai is an almost universal technique, although not very often named. Listen to tennis players, some kiai on every stroke. Listen carefully to boxers. Bill and JD and others who pump iron listen to the hardcore lifters pushing close to their limits.
One dojo I studied in kiaied on every repetition in a drill. It taught you to breath and , I think, was a great adjunct to conditioning.
I could go on, but you’ve all probably stopped reading already. One last thing, though–Jason hinted at the mythologies of Kiai; there are stories of masters of Kiai-jutsu knocking birds out trees with thier kiai, (although I always suspected serious halitosis). The idea is that a kiai can shock the system of your opponant/victim and/or drain their ki (or ch’i to you JD).
mabye the grunting does help hehehe