One of the problems of being good at something is that you tend to do it to the exclusion of everything else. I happen to be good at running, and it wasn't until I got injured and started training with kettlebells that I noticed that I had the flexibility of an 80-year-old. And I'm sorry, it doesn't matter how fast you are, if you have posture like this guy, it isn't sexy.
The fact is, most men don't stretch. I don't know if it's because yoga looks fruity, or because we think that more power in a narrow range of motion is better than being able to touch our toes. We might have lots of excuses, but there is little science backing us up. The fact is, stretching is good for every athlete. Ligaments and tendons in joints, especially ball-and-socket joints like the hips and shoulders, have crap for bloodflow. When they are injured (and all training produces micro-trauma in these connective tissues) and the body needs to repair the area, the white-blood cells, protein, and hormones necessary to do the repairs are flooded into the bursa sacs surrounding the joints. How do these materials get into the connective tissue from the bursa? Why, by moving the joint through its full range of motion! Stretching is doing just that. The end result is stronger, more injury-resistant joints that will help you stay away from repetitive stress injuries, nasty falls, and over-energetic kimuras.
While training for the RKC, I had to work on my joint mobility. In fact, I might have spent more time stretching than swinging bells. Kettlebells are an amazing tool for increasing your range of motion, but I found it necessary to add static stretching onto every one of my training sessions in order to correct the years I had neglected my joints. But I found something pretty amazing after these sessions: I felt freakin' great after them! Instead of feeling sore, tight, and exhausted like after my usual heavy lifting sessions, after a few minutes of stretching I felt brand, spankin' new. To quote a client of Jordan Vezina RKC, "I feel like I'm walking around in someone else's body!"
So when should you stretch? Always after your muscles are warm. Dynamic stretching that closely mimics the movements you are going to do in your workout should be done immediately after your warm up. I can show you a bunch of these dynamic stretches, just ask. But Static stretching (touching your toes, etc.) actually makes the muscles weaker and will impend heavy resistance training. So save those until after you are done. If you are looking to really increase your range of motion, talk to me about PNF stretching. That stuff is the shizzle.