[sexybaldman]

I would definitely say stretching is not the key factor in kicks, but it helps. You might want to try dynamic stretches which are leg swings. ALso, what others have posted is good too. DOing the kick slow and controlled allows you to strengthening the legs muscles and watch your technique. Make sure the technique is spot on and you should get all the power you need. And, if you are going to do passive stretching make sure it is after a workout and not before.