This past run I ran with a friend who does yoga religiously -- and she MADE us (my boyfriend and me) stretch after. It was pretty hilarious -- it was only 4 stretches, but she could do them to an extent of putting her head (or chest!) on her leg, etc. and we were sort of reaching down TOWARD our legs. However, we did these stretches for maybe 5-10 minutes after (just doing what she did -- as best we could) and, other than the knee thing, I had NO stiffness, etc. after. This was a first -- I usually get a "clicking" in the back of my calf, and some hip pain/tightness as well.