I'm way out of my league here since I don't really understand any of this stuff, but that's not what I'm reading from the others' posts (or from the article Alfonso posted).
I think the term "efficient movement" is confounding because it lacks a proper definition when we are using it -- it depends on how you measure it, doesn't it?
One might consider efficient to be using the least amount of energy (I'm talking physical/caloric energy here) used in order to perform a task. In that sense, simply lifting a finger without using anything else in your body may actually be the most efficient way. After all, it does seem like recruiting your entire body to lift a single spoon is kind of silly and overdoing it, isn't it?
Actually, I just thought of a better example. There was a period of time when I was obsessed with how I walked and thought about why people walk/run the way they naturally do as opposed to the way a TaiChi person might walk, or how a soldier might march... since the way people normally walk involves constantly losing and regaining our balance. And the answer was, well, the way we naturally walk is actually the most efficient way to walk and burns the least amount of energy. But it's certainly not the way an internal guy might tell you to walk.
Again, to fall back to that article -- just a thought: efficiency may not actually be a requirement for internal movement... efficiency in movement may result from high-level training in internal movement, but it's hardly the goal nor is it the defining measure (hey, the cause and effect thing I mentioned earlier again!). Things like whole-body movement and maintaining balance/equilibrium/groundpath at all times may be more important concepts to an internal artist than efficient movement. It might even be that... just like a neophyte in external movement needs to undergo a lot of training to move efficiently in an external fashion, a neophyte in internal movement also needs to move efficiently in an internal fashion. That is, a beginner of internal movement may actually be incredibly inefficient (especially compared to an intermediate external guy) and burning a ton of energy, but as they get better, they become more efficient at internal movement. Drawing from this, you might even have a case for saying that an expert in external movement may be moving equally efficiently as an expert in internal movement... but they're moving efficiently in different ways.
Again, I don't claim for any of this to be remotely true -- just a thought.
I think we agree about a lot of things here.
A question I have to ask though.
How can one recruit more muscle (muscles make power) and yet tax the system less (use less energy).
If this is not what we are talking about, then.
A) How does the body make force without using muscle.
B) How do you recruit less muscle and achieve more work?