Yes Meltdawn!
You are right! What you describe is what is called the “myotatic stretch reflex” This reflex action is a muscle contraction in response to sufficient froce encountered suddenly that cause it to stretch. it happens to prevent tearing of the muscles. Therefore it is a very powerful contraction, even more so than any consciously generated contraction. The first ppl. to do studies on this as the eastern european countries namely the Russians. They called it shock training, i think.
When we see how a tricep moves in a punch or chop in bai mei it becomes more clear. For all bai mei ppl. iam sure your teacher would say THROW ur punch out and let it snap back naturally, don’t pull it back, then quickly go into next move, right. When the tricep contracts and extends the arm ,as in punching, the force generated by the fast glyco. fibers is so powerful and quick that it snaps the forewarm backwards stretching the tricep, when this happens the “stretch reflex” contracts the muscle to stop the movement, b/c of special fibers called intrafusal fibers, surronded by nerves that sense this could damage the muscles. Since muscles have elastic qualities (as stated by meltdawn) they can store a portion of this energy generated by the stretch reflex and subsequent extention type contraction would be even more powerful. Research has shown that a muscle that is streched b4 a contraction will contract more forcefully and rapidly (Bosco & Komi, 1980 Influence of countermovement amplitude in potentiation of muscle movement). But in order to take advantage of the stored energy the subsequent muscle contraction MUST be smooth and done QUICKLY as possible. Otherwise look like taichi, LOL, just kiddin, no offense to TC ppl.
That is why bai mei moves are “jingy” like spring and done at top speed. Of course the ancients did not analyse this way. They were able to intuitively apply this with terms like Fa jing, qi, nei gung… But i still can’t figure out how other phenomenoms of qi works like bai mei iron shirt, LOL.