Mucho se está hablando sobre el origen de la fuerza interna desarrollada por Ueshiba en los foros. Dejo aquí un interesante post de Mark Murray publicado originalmente en aikiweb.
There is more than one power category when talking about Ueshiba. (I leave aside all the spiritual "myths")
1. The first is purely muscular. Ueshiba at his best before he met Takeda. The muscle power driving farming, carpentry, etc for most of the world. But, somehow, I doubt that this is the kind of power that Iwata Sensei, or Ellis for that matter, are focused.
This kind of power is mentioned by either Sagawa or some of his students. I had to give up power to get power. Sagawa could toss people like rag dolls when old but couldn't open a jar of food. Etc.
This kind of power can be used for MMA, BJJ, wrestling, and some jujutsu where muscle along with timing can replicate "hard within soft" or the radial tire analogy of rubber around steel.
2. Internal Power. No, not aiki. This is a power level generated by structure and frame and an internally built body. It is force generated from very little distance (if any). Even this can be divided into categories using "ground", "store and release", "whip", etc. Not all work the same but each can generate various levels of power depending on how well (i.e. the right training) the person has trained. This can be the power to snap bones.
3. The third ... for lack of a better term, let's call it aiki as learned from Takeda. This "power" of aiki can be generated between human bodies but not between a human and an inanimate object. It's best summed up by the Daito ryu men saying that aiki is making the other person do what you want ... but in a way that manifests softness without the requirement of timing. Power over another person in appropriately matching energy that comes out as ghosty feeling, running into a mountain that isn't moving, just being moved without a choice, etc. This is the true hard within soft, the rubber over steel, etc. all the way to completely soft and ghosty without resorting to timing.
#1 is fairly easy to accomplish, most people can attain it without tremendous effort, and it's something that a lot of martial artists have experienced. It isn't the kind of power that made Ueshiba famous.
#2 and #3, IMO, are what Takeda taught. He blended them together to create a very different martial body that most other martial artists didn't comprehend, but knew instantly in a hands-on experience that it was the "Holy Grail", if you will.
#2 alone wouldn't have done a whole lot of impressing. Yeah, someone has power, but so what? Given a good jujutsu man, or a good fighting man, try using that IP in a dynamic encounter against them. IP alone isn't going to impress 90%-100% of the time. Maybe half the time. Good jujutsu or fighting men will flow around with timing, sensitivity, and skills to negate a lot of openings to use IP, especially some of the slower IP generating methods.
#3 alone might have impressed people. Considering that the ghosty feeling and the being controlled would amount to creating a whole lot of martial openings for strikes and throws. But, that isn't the only thing we read about Ueshiba. As Ellis' article notes and as some of the students noted, Ueshiba had power in his grip. Ueshiba felt like a jolt of electricity at points in his life. He had juice and used it.
Can you separate out #2 and #3 from the aiki men? IMO, no. Not them (others, perhaps). They integrated both and used it in a "fighting" manner, with and without weapons. It was the combination of both that made other high ranking and skilled martial artists take note of them.
But, just how far did Ueshiba take those skills? Unfortunately, I don't have any answers for Ueshiba. Just all the myriad of articles about him.