I have always taught the body of Aikido as having two dimensions, rising and falling.
This can be elusive and is far more complex than just a strong powerful base and grounding and a relaxed upper.
One of my favourite quotes is “hands up, me down” (thanks Peter Ralston). This implies that when the upper ascends the lower descends. But it’s not just that they go in opposite directions, but that they do so in harmonious unison and synchronised velocity. This is the structure in motion, the bones and connective tissues, not the muscles pulling in these directions, but the skeleton moving inside the suite.
The suite is expanded and has tensegrity through breath and is always falling towards the earth(gravity), I always tell my students to imagine they are in the shower and water falls off every part of their structure towards the ground. The meat “hangs” off the bones. This expansion makes 6 directions of force, left right, up down, forward back – all in unison.
The legs don’t sink into the ground, they fall as if pushing the ground away from them, this is not pushing off the ground, but rather the heaviness associated with feeling like the friction point of the sole of the foot is generating rotation and maintaining maximum connection at all times to initiate the spirals of Aiki.
Non of this will come easy, and requires a sort of Shugyo where it becomes what we are rather than what we do.
Peter Kelly