I can't help much I'm afraid, but I'll try to help as best I can.
When you say animation, do you mean a video, or for low-poly game characters?
I plan on making animated movies at some point, and when the time comes, I'll probably do the following (the top ones, I'd do for in-game and movies):
I'd look at real life sources. It depends on what you want to make. You mentioned kung-fu movies, so I'll assume you want to make an action vid/game.
Look at how people move-not just the punch, but the rest of the body aswell. Try to act out the motion yourself when no-one's home(unless it happens to be a triple backflip spin-kick type thing
). Try to get a feel of which muscles move and which don't.
Watch alot of action films for inspiration. If you already have them, watch action films. I also reckon the action scenes in Buffy are pretty good too. It's on during the day on sky I think (not sure though-I don't have it).
Mainly a movie point:
Finally, remember 3D doesn't require stunt actors-your only limitations are time and imagination. Go crazy. Why have someone kick the bad guy in the face, when they can somersault it? There are no wires involved, so you don't have to worry about it looking all Crouching tiger-like. Final Fantasy VII: Advent Children is a great example of how this is put to use.
If you're talking about game animation, there are probably tutorials, but they're pretty rare unless you want a simple walking animation. I wouldn't bother studying the movement frame-by-frame either. It's low poly, so you can ignore slight movements. Watch out for major things like footing and what the other hand is doing though.
Sorry I couldn't be of more help. Maybe you could ask on the forums of the 3D software you use?