Is the eventual idea not to use local muscle groups at all?
If so, what muscle groups are making the power? I would guess from your post, and other discussions that we've had, that the 'ideal' muscle groups to be using (in this theory of use) are those in the core of the body.
Going back to the exercise of lifting a spoon, or indeed lifting anything (personally I prefer something like a pint of beer - good balance between effort and reward!).
This is an exercise that I originally got from Peter Ralston ("Art of Effortless Power" IIRC).
Start to lift the object.
Observe what happens in your body (note this is DIFFICULT).
Think about the physics of what *must* happen. e.g. In order to life any object the weight must pass through your body to the ground. What does "pass through your body" mean? How does your body adapt to this? What muscles are pre-stressed to accomplish this action? What happens to adjust to any extra load occasioned by the action of "picking up" something else?
Next exercise, imagine you are *about* to pick up said object, and intend to do so, but stop before anything moves (i.e. your hand which has grasped said object). If you fully intended to move but stopped, analyze what did actually happen in your body - which muscles fired, what weight shifted etc. Your brain/body organizes all this stuff automatically, pretty much every time we move - but we are generally totally unaware of what is happening.
Apply this approach to different weights of object and see what happens.
For you to lift *anything*, even something as small as a spoon (or indeed any part of your anatomy such as a finger, a hand, any part of your arm without any further load required), then the load *must* (due to physics) pass through the load bearing structure (your body) to the point of contact with the ground (e.g. feet, or perhaps your butt if you are sitting on a chair) - assuming of course you are on the earth as opposed to being in space!
This is difficult stuff because it requires so much attention to detail. We imagine that we "just use our fingers" to pick up a spoon, because we are not aware of all the other stuff that goes on to transfer the weight through our body to the ground. When we start to become more aware of what is really going on, we can start to become more effective.
I suggest that until you become in some sense at least aware of what *really is happening* within your body right now every time you move anything, it doesn't make much sense to worry about what are the most effective muscles or muscle groups to use.
Does that make sense?