I personally have found that kokyu is one of the most important principles in the practical application of the art, yet there seems to be much misunderstanding and confusion as to what it really means. Part of the problem I see in western aikido is the explanation of Japanese concepts in English. Many people use terminology such as "extend your ki", and "feel your energy" when describing kokyu. These are good efforts I believe, but sound mysterious, and doubtful as these are terms not common in explaining physical movement. As a result, I often see beginners with a big question mark above their head (Extend my what???, oh, OK, I saw this on Dragonball Z!) Kokyu "power" ends up sounding a lot like using the "force".
Another approach is to use physical demonstrations such as the "unbendable arm". However, this raises questions such as, is the person really applying the same pressure in both circumstances (when the arm is held using physical strength vs. kokyu power), and is the other person allowing their arm to bend, perhaps, even subconsciously?
I would like to ask if anyone has for the first approach, a more grounded and understandable explanation for kokyu, or for the second approach, other physical exercises which might help more to convey the feeling of kokyu.
Thank you in advance for any input.