There are many details to effective kime, which obviously have to come together to the point that you just have the intention of finish technique, and all the details will happen by themselves. At this point your body knows how to make kime.
But no matter at what level we are we always have to revisit and reflect if we apply all aspects of kime optimally, we can always get better. Sensei Nishiyama was never tired or bored of repeating the principles and details of kime, and there was always something subtle, new, that could be learned.
Breathing “through pass” target, “give all air, give all energy”, Kiai destroy opponent”
Those are different ways to describe a similar aspect of kime. This is an aspect of kime that is difficult for many people, to mentally give everything, and to give all air through pass target, which means all energy and momentum transfer to opponent. Actually, giving all air is a mean to give oneself totally, not to hold back anything, as budo says “no mind in the technique”.
Giving all air is giving all energy, as Nishiyama Sensei used to say “one period of breath is total amount of energy”, it should be done in the shortest time, and is only effective when the breath matches with the technique, and than at impact there will be maximum pressure to floor and total body contraction to technique line.
Make sure not to blow the air, but pressure to floor and as reaction air goes out, than your throat will stay soft, the breath is not in the throat, the throat is just like a pipe. The breath/kiai peaks at impact but does not stop, don’t push we need shocking power.
When one gives all air, next breath starts as reaction, therefore next technique or kamae starts naturally (zanshin), you don’t do it, it is done by itself.
Giving all air solves the problem of “snap back”, since “snap back” happens when half the breath (energy) goes to technique and the other half (of breath/energy) goes for the pull back, which means that only part of the energy goes to the target.
At the same token one should not stop and hold the arm extended, this is a dead arm, and it is a space for opponent to counter.
Giving all air solves this problem as well, since when you give all air, next technique starts as a reaction, and you don’t cut and stop at kime.
“Snap back” is especially bad since while “snap back” the momentum is going back, there is one extra motion, space between techniques, which the opponent can capitalize on.
In any case, the more skillful a person is, the shorter the instant of kime is, and one can give all air and deliver all energy in shortest amount of time.
“Give all air” is a feel, and is changing depending on the technique, target and purpose.
Tsuki (punch) to the face is different than to the body, when punching the body more penetration is required and deeper kime, while the head gives, and impact need to be sharper, so energy is transfer before the head gives, even when looks like snap back, all energy must be tranfered first, even in striking techniques (uchi waza).
The point is that once the momentum is delivered there is no point to stay, next technique or kamae are transitioned to naturally, as reaction.
“Snap back” usually happens because one protects itself, wants to recover quickly, but when the chance is there and you are ahead of opponent, no worry, you must try to finish.
“Snap back” also happens when the breath cuts and the body bounce, and “snap back” results.
“Snap back” is also result of sport karate competition, when scoring is awarded for just reaching the target. Those kind of rules encourage training for just reaching the target with the fist, not passing through with the whole body.
It is, of course, easy to reach the target with just the fist than with the whole body connected and total momentum delivered to target.
Some ideas of how to give all breath and energy through target:
Before technique, look way beyond the opponent, intention beyond opponent to infinity, your feet stop inside opponent but breath continue through, it should feel as if your body wants to keep going, yet your feet holding the body from going. If you look to the spot you hit, your breath/energy will stop there.
Another idea, feel as if your body stops yet inside your body continue through opponent.
Another idea, Imagine your kiai has no echo, the sound does not come back, I like this idea a lot, Sensei Nishiyama told me this over and over.
Another idea, think not of poking the opponent but rather thrust a spear through.