Robert M Watson Jr
This is not representative of any conservation of energy principle from western physics that I'm aware of. 'Potential human energy' of course needs to be more clearly defined but 'intent' has no where near energy to transform into substantial muscular motion.
If folks want to use the rules of physics then they have to follow the rules and not just make nifty sounding analogies. Of course, one does not need to know the rules of physics to follow them! Those who are familiar with the rules can see when they are not being used properly as easily and surely as ones teacher can tell when correct practice has not been done sufficiently (presuming they actually know).
I could care less is someone cannot explain things using the rules of physics but when they try and make a mess of it it does not help anyone. For all I know Shen-Yi-Chi-Li is all the explanation that is required (and may even be correct) but it ain't an example of conservation of energy.
I'm a strong advocate of a 'unification' of eastern and western practices and ideals (we call all only benefit from it) but it must be correct as viewed from both perspectives. If there is no unification on some points then one or maybe both perspectives are actually wrong (this would be a statement of principle).
Principles can be wrong as well.
Well, that quote was a classic, in my opinion. I get so used to seeing all the mangled claims in Asian martial arts that I quit paying close attention some time back. Basically, the student mangled what was going on and I don't think that Cheuk Fung's grasp of English or Physics is enough to help out.
Throw out the student's question (based on his perception of what Fung has tried to say in the past, apparently). What Cheuk Fung's trying to say has little to do with the conservation of energy (and it really doesn't explain much, even though it sounds nice). What he's explaining is the classical concept of how movement works in the qi-paradigm. While the qi-paradigm didn't fully work out (it's more explicative than it's predictive), the observation about movement isn't a bad one.
Incidentally, the student perhaps should have transcribed the interview so that it says "Xin to Yi to Qi to Li". It's the same "Xin" that equates in Japanese to "Shin", as in "Shin Shin Toitsu Aikido".
Basically, what Cheuk is saying is that in the old perspective there is a "desire" to do something (like a punch, for instance) and that "desire" triggers (via the mind "intent") the "qi" which alterations within the body which in turn result in a tangible force (Li). Look at the "Cast in Resin" posts on QiJin if you want to see a more extended discussion of functional reality.
If you look at O-Sensei's writings, he mentions the same classical perception in his discussions about the "Divine Intent". Ueshiba's and Tohei's ki-demonstrations are considered to be classical examples of that very phenomenon, too.
But, the main response to your (valid) comment is that the student simply misunderstands what Cheuk Fung is talking about.
Oh, as a side note, "Hunyuan" training actually relates to 3-dimensional stressors on each "molecule" (if you will) of the body, done by setting up jin using the mind-intent.