... rowing, ......while trunk twisting warm-ups, ..."windings" from my opposite thighs and/or feet. ...
undefuri ... "upper cross" ... trunk windings as well).
yes -- yes -- yes -- and well -- yes.
I practice "aiki-age" during ushiro tekubitori kokyunages ... instant ikkyo effect
When I am grabbed katatetori, I practice "center on contact" using good structure/intentions and the "trunk windings around the spine" (a.k.a"central pivot").
We practiced juji tonight with the bokken and then moved into the same with ikkyo, and then sankyo just for some osae work. The opening was with yokote engaged. If the blades remain parallel it is ai-uchi -- and uchitachi has no incentive to stay without the dominant line. But if the line is left slightly open, by letting the tsuka drift one side while the kissaki drifts opposite and musubi is maintained, then uchitachi has what appears to be a dominant line. It is the position that uchitachi would have placed you in to clear the line to enter for tsuki or tegiri. It is, of course -- a lie.
Where is juji, you ask? Simple. The kissaki in chudan is at 12 o'clock relative to the tsuka. If uchitachi did what he wanted -he would reorient my kissaki to the 3 o'clock position (my perspective) opening the line. But if I am already in the 3'oclock position I am in juji -- 90 degrees phase difference -- which creates a resonant relationship between the two dynamics as they are engaged.
Now where is the aiki ? When he moves in (or I move in, same thing: 90 degrees phase difference makes sente essentially irrelevant) I slightly center both the kissaki and the tsuka using the same "winding" projected from my center through the tsuka and out the end of the blade. His blade ends up off my left sleeve and mine is in his throat
Now I can do the same thing with far less gross movement of the blade, and while appearing to remain parallel and in ai-uchi relation. It is "internal" in the sense that the reorientation occurs inside the point of engagement, and transmitting the "winding" is not directly apparent to the opponent, because it is oriented perpendicularly (spatially and temporally). It is adopting the form in initial "static" structure that the "winding" would drive dynamically -- i.e. -- they are really not different at all. The entry and the "winding" happen together, i.e -- it is irimi-tenkan.
Then we examined the same principle substituting the use of tegatana in ikkyo -- centering on contact, and the same reorientation of the arm maintaining tegatana) from 12 to 3 ( or vice versa depending) (closing the waki as is very often the case in techniques demonstrated to ushiro tekubitori.)