Raul Rodrigo wrote:
Lets back up a bit. If Shioda didn't the exposure to the internal Chinese arts that Mike S and the others have, how did he develop this understanding of the big toe? Through misogi breathing? through funekogi and furitama? The eyewitness accounts of the Kobukan dojo that I know of describe years of hard physical training, and very little by way of internal development. I know that some later deshi like Tohei and Tada and a few others went to the Tempukai, so their understanding of internal power is more advanced. Did Shioda go? Did he have some internal training that we are not aware of?
That's a good question. I can't do anything but speculate, but this thing you're talking about is probably a carry-over from Japanese fencing. You can actually do it with either leg, but I suspect in the Japanese usage it originally developed as something from the forward-shifted fencing posture that keeps the sword as far forward as possible in order that the front leg, etc., can't be attacked.
In a way, what you're asking is part of the "bounce" mechanism of both Ueshiba and Master Sum in those 2 videos. As you notice in the videos, it is not leg-specific, but from experience I'd say that the smartest thing to do is start learning it with the back leg.