Thanks for your thoughtful reply, Charles.
charles wrote:One can generate force - "long" or "short" - by expansion/opening or by contraction/closing. In both of these there is sinking of the body, but at different points in the sequence. The arms should always be "relaxed", but not limp, regardless of opening or closing. So, your description doesn't, for me, isn't what distinguishes long from short power.
In some styles, the entire body doesn't do one thing. That is, parts of the body do one thing, open or close, while parts of the body do another, open or close, but in a coordinated way. In that case, some parts open, some close, some expand, some contract. That can be done while shifting weight or not.
I kept my description short because I wanted to make brief points, not make it into a long post. In principle I would certainly agree with the opening and closing, expanding and contracting. For instance, area between the shoulder blades opening and chest closing. To some extent I do this, but quite possibly I don't (or can't
) do some things in the way you envisage. Probably too hard to explain in words - a pity you can't show (me) this in person!
If A can then project B backwards with a clear push and maintaining relaxed arms without A himself falling (or swaying) forwards or backwards in the process, then I find this translates quite well into short power.!
charles wrote:The salient point of the exercise you describe seems to be that there is no linear translation of the centreline, per Bao's point. There are probably lots of ways one could describe the distinction between long and short power. Bao's description captures some of that with his stating that long power involves follow-through and a translation (weight shift between legs) of the centreline, while short power doesn't. That distinction works for styles that do shift weight while pushing, but doesn't include those that don't (e.g. Hong style). In other words, its possible to push (long power) without necessarily shifting weight.
Agreed. IMO the forward shifting of the centreline (and often sinking it simultaneously) is very common for long power but not strictly necessary (see below).
charles wrote:As you pointed out, duration of force transfer is one of the distinctions between long and short power. Another is that in long power, the object is to move the opponent through a distance; in short power the object is not to move the opponent.
...but to make the energy stay inside the opponent.
Agreed, whereby I'd say that the second difference is a natural consequence of the first. To illustrate the basic physics with a theoretical (and rather macabre) example: You have a long steel rod of 1cm diameter and a flat end. You can place the end against the belly of a person and apply force in a forward direction and in a smooth manner over, say, 5 seconds and in this way push him backwards 1 metre. If you then apply the same amount of force in the space of one-quarter of a second, the person won't be moved backwards, but something else will happen. The 'penetrating power' here is more literal of course, but also a metaphor for short-power strike.
A short video demonstrating/explaining your approach(es) would be a nice departure point for further discussion. Just a thought...