You should never stretch cold because you run the risk of pulling a muscle. Do a quick warm up, then stretch and then do your workout. Warm down and stretch again before you finish.Back when I used to run cross-country we used to do a half mile warm up, stretch for a good amount of time, run 5-8 miles, and then cool down a quarter to a half mile. We followed that with another stretch and ice cups for the knees :icon_smil.
Honestly, as a biology major, I can tell you that there really is no conclusive research done for whether or not stretching prevents injury, period, regardless of whether you do it before or after your workout.http://www.webmd.com/fitness-exercise/guide/top-20-fitness-mistakes-beginners-make
10. Stretching cold muscles. Stretching before your workout puts you at risk for pulled or torn muscles. "Always stretch at the end of your workout," says Pillarella.
11. Bouncing. Bouncing during a stretch can increase your risk of straining or pulling muscles, Pillarella says. Instead, "hold a static stretch with no movement at the joints. Your body should feel lengthened but not to the point of pain."
What I am trying to point out is that the muscles need to be warmed-up before being stretched...