“Never tense koshi.” To do that, you should not become conscious of koshi. Your thinking about koshi will make it tense, and thus, a disconnect between the upper and the lower parts of the body occurs. That is not “using the whole body.”
Hino , Akira . Don’t Think, Listen to the Body!
There are of course several issues when concentrating too much on kyokotsu. When your kyokotsu movement is exaggerated, your shoulders tend to move forward. The result will be a lesser movement within the koshi and/or your neck will be placed unnaturally.
You need to understand that kyokotsu is the center of body motion control. By moving kyokotsu there will be mainly moving in 2 areas of the vertebral column possible.
- neck region
- lower back region
Impact of kyokotsu movement on koshi
As the headline of this article suggests, it is the impact of kyokotsu on koshi.
If the kyokotsu is slightly drawn, the lower part of the spine is pushed outwards and downward. The result is the rotation of the pelvis, although the focus is on pulling in the kyokotsu.
Imagine a cord tied to kyokotsu and koshi (lower back). If you move the chord to the kyokotsu, it will affect the pelvis.
Pushing or attacking
When there is the intention to attack or pushing forward, kyokotsu will be pulled in at the beginning of the action. There is the reversal of the basin. But there is also the effect of the opposite isometric tension in the leg. It creates a powerful bounce and is added to the basin ready to be used for attack or push.
Kyokotsu, koshi and rolling feet
Starting from the situation of lifting the arm and preparing for the attack, the use of rolling feet is the method to close the distance to the attack as well as using kyokotsu and koshi.
Study Group Tomiki Aikido 