A proper karate stance should be a perfect mix between mobility and solidity. Mobiity is when one can launch their body quickly. Solidity is when one can grip the ground with their feet and not be moved.
In the Shotokan kokutsu dachi stance, however, the ability to be mobile or solid has been compromised. If you study the feet you will see that they are pointing in directions that are more than ninety degrees apart. This means the stance can’t make up its mind whether it is supposed to be mobile or solid.
If the rear foot is angling away from the target the major muscles are not pointing towards the target. The foot being in the incorrect position means that there is not going to be enough traction for the foot. The leg being pointed in the wrong direction means that the major thrusting muscles of the leg can’t be properly utilized.
in addition, the hips won’t be facing the right way, and when one pushes with the leg there will be an ‘energy leak,’ in the body. That is to say that the hips will not be strong enough to maintain the energy of the push. This can be severe enough to weaken the back, and even (in rare cases) lead to damage to the lower back.
To fix this stance all one needs to do is turn the rear foot to about 45 degrees or less towards the target. This will set up the foot for more traction, and set up the major muscles for the push when one launches oneself towards the target. Of course, this is going to alter the fundamental nature of the stance.
Thus, when you turn the foot properly, you are going to have to figure out the angle of the hips, and set the weight more on the back leg. Doing this will set the body for maximum push, but shotokan instructors will resist this alignment of the body for one simple reason: it lacks shotokan power. But this means that the system has been corrupted for the feeling and sake of power, and not for the balance between grounding and thrusting.
To get past this, Shotokan masters have set the system up to rely on overly aggressive front stances. What they have done is okay, but only in specific instance, and the proof is in the fact that the kokutsu dachi stance is more for rooting than for shooting. Thus, you have a choice at this point, do what you are told in Shotokan Karate, or other classical martial arts styles, or analyze the physics I have presented here and alter your stance in accordance with these physics.
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