Total body, mind and spirit integration
The essence and principles of the sword create the art of Aikido. It’s not the physical lifting and falling of the sword, but the body movement principles that are intrinsic to the functioning of speceific techniques.
This principle relates to the sole of the foot and how it rotates the hara into instantaneous multidirectional movement. For example, kirikaeshi can be done as two seperate movements(as most people do it), or in a single instant movement where forward and back are one.
The latter takes years of training and changing how western people think body movement is done vs how it can be done.
When the founder said “the feet reveal the secrets of the universe”, he wasn’t just talking about where you put your feet, but how to utilise them and there tactile, manipulative, versatile connection to the ground to influence the point of contact between two forces.
I have seen Maruyama sensei on at least 4 occasions draw an image of the sole of the foot/feet to explain how the body functions in aikido from the feet and how they communicate to the ground and connect through the structure to the point of contact. Small hand and shoulder blade and arm pit functions (all aspects of Yuishinkai body principles) are useless without the ground path that creates their functionality.
Aikido is just gross motor skills or it is TOTAL body, mind and spirit integration. Shin shin toitsu isn’t part of body integration it’s total body.
Total means not forsaking any part.