Is stretching necessary before and after exercise?

During a discussion at work about stretching before and after exercise one of my collegues said “there’s no scientific proof stretching does any good to your training”. I’ve sported most of my years growing up and stretching before and after exercise has always been considered common sense. However, if I’m not sure about something I’m not ready to stand up for it in a discussion, so I just replied “I didn’t know”. This happened half a year ago and since then I’ve been just doing my runs with stretchings involved as usual.

But today I thought maybe I should look that one up on Internet. What I stumbled over was these articles which I find fascinating

The truth about stretching by jason Heavey
Stretching, flexibility, hamstrings and injury by Jim Bledsoe
Phys Ed: How Necessary Is Stretching? by Gretchen Reynolds
Stretching: The Truth by Gretchen Reynolds

The latter of them even suggests that conventional stretching before workout weakens the muscles temporarily. However the first two of them suggests that stretching after exercise is a good thing that makes muscles flexible and helps recovery.

On the other hand Stretching: The truth suggests that warm-up exercises before a workout is crucial to avoid injuries. There are even a few examples there.

I’m not the first one to throw myself at something just because I’ve read an article or two, but I truly find it intriguing stretching might not do as much as we believe. I’m at least willing to go further in my research.