I have been using both a bouncing and static stretch. Now I have heard for a long time that a bouncing stretch is bad and you should not bounce during a stretch. But I have seen others do it and I also bounce sometimes depending on how it feels and it feels fine lately. I used to never do bounce stretch because I heard it was bad , but I 'm feeling ok with it, it feels like a compliment to my static stretch. So the question is ; is bouncing stretch bad???
Bouncing is very old school and not something that you'll find the new breed of coaches doing. It's worth taking a look at Van Zandt's stickied threads in the flexibility forum. Take a look too at this site, which will explain the differences between static, dynamic, ballistic and other types of stretching methods.
When bouncing, you're continually provoking stretch reflex: http://en.wikipedia.org/wiki/Stretch_reflex
kind of related so here's a little research paper (citation only) to consider: Moreside*, J.M. and McGill, S.M. (2013) Improvements in hip flexibility and/or core stability does not transfer to mobility in functional movement patterns. J. Strength & Condit. Research. 27(10):2635-2643. they suggest that you slowly work up to full range of motion in the specific task (e.g. mobility for kicking, you would work on the specific kicking movement pattern)
Ive read the articles Simon pointed out and the wiki on stretch reflex. Im still not totally convinced stretching is an exact science. For one thing I feel that when I bounce in an inching slight way it feels like it gives my tendons more pliability. Which gives my kick more power for example...I am experimenting with it. Ive done some yoga and that's also good stuff. no bouncing there of course. Its a work in progress. Always take the safest way if your unsure I guess.
One problem with bouncing is the risk of injury (and continuous small scale injury). I read somewhere (although can't remember where. May have been MAP) that bouncing with your stretching tears your muscles just a bit every time, eventually leading to internal scar tissue that can cause all sorts of issues. Or you could just strain your muscle while stretching, that's why I stopped bouncing. I could be making up that scar tissue thing, I just got off working all night so I'm very tired and possibly getting mixed up.
You shouldn't bounce but dynamic stretches are great. Like a leg swing, don't explode your peg up and tear something! Just slowly and lightly swing back and forth, under control. As you do more you gentle push further in the swing and will increase your range of motion.
Stretching is not an exact science. Nothing related to the human body is - we are not machines. If everything was an exact science, we'd all be Olympic level decathletes able to drop into the splits and stave off injury, disease and old age. But we can get pretty darn close As for bouncing... don't.