Re: Kokyu explanation
Just to muddy up the waters a bit more, let me comment once again that "ki" and "kokyu" are inextricably intertwined. Technically, kokyu ryoku is the physical manifestation of ki. In that sense, Tohei can stand with his forearm proffered (ready for his partner to push on the forearm in order to exhibit a rooted stance) and he has "ki" to his forearm. Once the partner physically pushes against the forearm and feels the actual path of power, Tohei is exhibiting either his "ki" or his "kokyu", depending on your fancy. If Tohei stores and releases along the path through his forearm into the pushing uke, he is exhibiting kokyu ryoku, as the Japanese use the term.
The essential power of kokyu depends on (1.) paths the mind sets up and also on a (2.) body-skill/development that is done largely by breathing training and control. The major nexus of that power is in the hara area, but it also extends out to the ends of the limbs, with training. Because the real power of the kokyu paths depends so much on this training with the breath, it can rightfully be called a "breath power". From various descriptions and sources of Abe's focus, I have no doubt that he knows and has developed this basic power source of "ki" quite well. And he knows how to use it.
One of the side-effects of this kind of development is an increase in good health... and I've personally seen this happen to me and others, so when someone says that Abe Sensei exhibits unusually good health and strength even at 90 years, my inclination is to attribute a lot of it to the development and use of this training. Remember that Shioda and Ueshiba also both indicated that these studies were focused somewhat on quality of life as they got older.