This thread is suddenly good again so I'll subscribe by answering the long-dead original poster (if not dead, apologies
We are told that nikajo should not be painful in the wrist. This is a difficult effect to produce, but as uke, I have felt times when the only thing I noticed was my hip and knee collapsing--no pain response.
In the past I have felt budoka from different martial arts trying to apply this technique--nikyo, I believe, in Aikikai. I always thought it was supposed to hurt at the wrist, and the problems people always had were in avoiding collapsing the arm.
Does Aikikai try to produce pain at the wrist?
I have no idea what Aikikai tries. It is an governing organisation, no?.
for me Nickyo hurts, I apply it to hurt & control at the same time, and long training and/or genetics can significanly reduce the hurt from all variations of Nickyo.