Running

I don't stretch beforehand. I found it was doing more harm than good since I was cold.
The best option (for me) would be to come back from a ride or do turbo and THEN stretch and then run. Perfecto!

look up dynamic stretching,

its what you see footballers & track runners doing all the time. Static stretching increases your range of motion but does nothing to give you stbaility/strength with it.

So it can actually lead to more injuries, plus it kills a lot of the muscle rebound which you can use to your advantage, also making you slower.