Re: Push Test to Nikkyo
We would call this a "centering exercise" or standing kokyu tanden ho.
I use nikkyo ideally to show how the legs may be buckled (aiki-sage) by the flexor reflex before uke is quite conscious of the fact -- the joint lock is wholly secondary and resulting from the action, not the means of accomplishing it. Nikkyo, for me, is a lesson in how one form of that action works -- how it is triggered and how to judge its correct application. Sankyo is the converse -- triggering extensors (aiki-age), FWIW.
What is shown is a rather different manner of nikkyo -- very linear. That is not necessarily problematic, as it can create more instantaneous local buckling behavior at the connection, but that does not appear to be used -- again not necessarily problematic either -- depending on the situationally appopriate use of that connection. Instead, the connection is used to carry uke off his base of support, the "toppling" result in the uke -- rather than buckling the support as in aiki-age, or "springing" it aiki-sage. In fact the more linear nature of the connection shown, and the direction of the longitudinal rotations used is closer, structurally, to a sankyo and which thus sees just a bit of the "springing" reflex behavior in the calves and ankles, mixed in.
Correct rhythm of action is a key aspect of the most effective nikkyo, IMO. The registering of any pain from the applied lock is an afterthought to the triggering of the undercarriage flexor reflex -- which should precede it. As I see it, if uke does not find himself compromised involuntarily before pain is really perceived, it is not ideal. Purest ideal is provoking the reflex with little or no pain sensation at all.
But the order of perception is a good objective gauge of success in developing correct action -- because the spinal reflexes are faster than the cortical pain relays. If you are not getting true reflex action from the connection, then pain is felt ahead of or simultaneous with the body's reaction, and the reflex, if present, is thus mixed with voluntary neuro-muscular stuff, which can override reflex in whole or in part. Lagging pain sensation is a very good test of more "pure" reflex action, from my perspective -- which cannot be easily overridden if triggered in isolation.
Anyway, thems my thoughts and thanks for the video.