This has been a long going debate since I was in college. My roommate was a sprinter on the track team and some of her coaches would make her stretch while others were completely against the idea. She hated those days when she wasn't allowed to stretch before hand because it always made her feel more relaxed and more ready for the practice.
I will admit that through my own training I have regularly heard that pre-stretching was a no-no. The idea is that stretching loosens muscles, tendons and other connective tissues and in theory would lead to more injuries during running.
And while it is true that you shouldn't do static stretches before a weight training workout for this reason, when it comes to hitting the roads for a run, new research shows it doesn't matter one way or another.
STRETCHING BEFORE RUNNING
I like this because I don't stretch, I tie my shoes and hit the road (I lack patience for holding poses while my running playlist is calling my name).
The recent study watched 2700 recreation runners who run 10+ miles a week. Half of them were set on a stretching regiment right before runs and the other group avoided the toe touches. And the results showed that neither group was more prone than the other to injuries.
What did affect the injury rate was:
History of chronic injuries or injury in the past 4 months
High BMI
Switching up the routine: Making non stretchers stretch and stretchers not stretch.
The lesson is just stick to what you prefer. If you stretch before then don't stop and if you don't then don't start now. You're better off!
STRETCHING BEFORE LIFTING
I already said above that when it comes to weight lifting it's best to avoid static stretches at the beginning. There is a correlation between stretching and injuries. But it shouldn't be avoided all together.
You should spend about five minutes at the end of your workout doing a few static stretches. This helps return your body to a normal state after an intense workout and helps you see results faster.
In fact, studies show that stretching post workout helps to promote muscle recovery and rebuilding. It helps the muscles heal and tone up faster basically. Stretch and get more toned and more lean! It also helps to relax you and your body so you can go on with the day feeling wonderful.
I stress multiple times a day to help blood circulate throughout and to help me relax after training clients and looking at a computer screen.
Here is a video I did not too long ago on some stretches to help you out!