In another thread,
What is ki?
Does it only exist within the fascia? How do we know?
How does it flow?
How is ki related to "IP/IT/IS"?
What is its function?
How does it flow? That's an interesting question. It leads to another: "Why do we even think that it does flow?"
The answer, of course is that, "Well...everyone says it flows."
And who said that first?
It must have been the taoists and creators of traditional Chinese medicine.
Acupuncture and shiatsu are both based on the theory that qi (ki) flows through the body in regular cycles along well established pathways with "points" at which the flow may be sped up, slowed down or stopped. This has been shown to ease inflammation, invigorate weak organs or eliminate pain for dental or surgical application. So I am impressed that their theory has substance.
My understanding of this is that, since ki is life energy itself, it has to be in the whole body all the time or the part where it was not would die, which is an irreversible process. So life has to be in the whole body all at once. But it also moves through the body and an expert Chinese doctor can tell exactly where it is in the body at any moment. If this seems strange, then explain the question of locating a "nuclear particle" at any particular instant. The nuclear "particle" has been explained as actually being a spherical "shell" of energy that "condenses" at a given location on the sphere to appear as a "particle" but it is really more like a wave in a body of water, a movement within a substance which appears fleetingly at one place, then another. So I see ki as being both everywhere in the body at once, all the time, but also being somehow concentrated at a point that move in a regular cycle through the various meridians of the body.
On the other hand, for IP/IT/IS, we can use the mind to direct the ki to any part of the body instantly. And that directing is an expression of intent. But while ki is never released from the body, intent can extend to infinity, which can have a great effect on someone has no strong ability to focus his intent.
As for actual physical delivery of power, I don't think there's really a difference in what reaches the attacker, only the purity of it. And that means purity of force.
Rob John addresses this in his thread on "Weight Transfer." The question is how to get "all" of your intended effort to the target without losing a lot through disorganization.
Supposedly, Ark tells people their nervous systems are like dial-up internet connections while he is using fiber optics. It's not that his nervous system is really different but IP/IS work is really largely about "connecting the dots" so that both information and power flow within the body without confusion or blockage. Here an analogy to water might be better than electricity. While your electrical connections can be good or bad, there's either current going or not. If we consider water, imagine that your main line puts water into a sump type of place where the open ends of the pipes to the rest of the house have open ends. When you turn on the water, the main line starts filling the sump until it gets high enough flow into the other pipes of the house. You can imagine that when you turn on your shower, the water flow will be pretty poor. The problem is that while the water can get from the main to the shower line, it's not properly connected. You won't get out what you expect at the end and you'll lose water in the process.
The body/mind organization of most people is a lot like that. A push from the foot loses effectiveness in the foot first, then the ankle, up the leg, in the lower back, etc., etc., losing a little more at each point so that it's quite weak at the end. IP/IT is concerned, among other things, with getting all the connections "tightened up." Actually, I think the usual term is "take the slack out" because being "tight" is not what we want. But we want a firm connection and maybe a little stretched but not strained.
This process can be undertaken entirely by "the mind" but its nature does not allow it to reach directly into the body. If the mind attempts to understand the body, it has to work within its own rules. It does some things and doesn't do others. For one thing, the mind does not "feel." This is an important place where we can clearly distinguish mind and ki. The ki, in IP/IS, is used to "feel" within the body without having to have some nerve impulse. The mind can detect both nerve impulse and the "feelings" of ki. Usually, people believe that it is the mind that is feeling, but it is not. The nerves feel and the ki feels, but the mind can only receive the impressions from those feelings and it organizes that information and takes action on it.
So we use the ki to let the mind in on the deeper secrets of the body and in that way, through serious effort, the mind "becomes one" with the body because it can enter any place in the body through the ki.
When the mind and the ki work together, the mind can penetrate the entire body and can recognize where connections are too slack.
Going beyond just this basic outline sketch, you need a real teacher to show you directly what's what but I think this is a good entre for putting these concepts into perspective and place.