We have 2 type of stance: kime stance and kamae stance.
Here I discuss some elements of kime stance, the stance at moment of impact, which is most prevalent in the kata.
We have 2 types of kime stance: outside tension and inside tension.
Outside tension stances are most common in shotokan (zenkutsu dachi, kokutsu dachi, kiba dachi and sochin dachi) even though we use inside tension stances (Hangetsu dachi, sanchin dachi and neko ashi dachi) quite often.
In an outside tension stance, at kime the muscles of the hips and thighs are contracting from the outside in and toward the centerline of the body.
In an inside tension stance the muscles of the hips and thighs are contracting inwardly toward the front and the midline of the body.
The purpose of this contraction is to make a strong base in order to fully deliver the technique’s power through target, and avoid recoil, bounce of energy as reaction from impact. The contraction of the legs and hips allow for strong connection and transfer of energy from legs through the body center. Of course there are some other reasons such as contraction is potential energy, kime should be best condition to starting next action.
Bones not moving
The bones of the thighs are not moving; rather the muscles are contracting around the thighbones and pelvis.
If the bones are moving, the thighbones will be out of optimal alignment with the hip sockets, and as result, transfer of energy at the hip joint will not be complete, and there will be undue stress on the hip joint, which over time can result in injury.
Contraction must have direction
The contraction of the legs and hips muscles is not static, since power needs direction. The contraction is either from the outside or inside toward the centerline of the body and in a spiral to the line of technique.
In a case of a punch for example the contraction of the legs and hips is in a spiral from the ground up to the technique line.
In a case of pull, or sweeping block, the contraction of the legs is in a spiral toward the ground, this is what we call reverse transmission of energy.
Stance contraction allows for total body contraction
We know that at kime we need total body musculature contraction in shortest time to line of technique. If the legs contraction is insufficient than the rest of the body contraction will lack, since the stance is the foundation.
When practice kata, try to move at full speed and at kime legs don’t move, not any wobble. Remember that when the outside stop, the inside energy don’t stop.