Just as an observation: A lot of the talk about "Internal Strength" and "Aiki", etc., appears sort of new and exotic to a lot of Aikidoists, but I noticed in "This is Aikido" and other early publications, there was a lot of discussion about "ki strength", "kokyu", and so on. They were talking about the same thing.
In a lot of Asian martial arts it's been my experience that many westerners get confused by what appears to be different terms and think therefore it must be different topics. In many cases, as Shioda noted, they're talking about the same thing but with "different names". And often, when done correctly, there appears to be very different training methodologies when in fact all that is often seen (in correct training) is simply a different attempt to explain the same physical principle. What goes wrong is when someone grabs the buzzwords and attaches their own meaning to it; hence my caveat about 'when done correctly' (not to be confused with 'when done strongly enough to kick your butt', which is what basically hamstrung much of American and European Taiji).
Such is the case in all endeavors in life and the largest impediment
in communications between people.