Stretching after training has been crucial for me --- I've got a rotated pelvis which I've gotten addressed thru 3 months of rehab w/ my chiro last year -- but it leaves me w/ a ridiculously tight psoas / hamstring on my left side. Yoga has been a big part of my training this year as well. I do a mininum of 5 min cardio warm-up before I lift and if i do anything upper body, I do a couple giant sets of rotator cuff warm-ups. If I don't' warm that up, I've had whole sides of my upper body get all messed up trying to compensate for the pain and that just doesn't fix anything.
Stretching is basically just a great way to "come back down" from training. You are still warmed up but instead of just stopping cold. you take the time to let everything relax some and stretch the muscles out.
Here's from a great stretching source by Brad Appleton (
http://www.cmcrossroads.com/bradapp/docs/rec/stretching/stretching_5.html):
When done properly, stretching can do more than just increase flexibility. According to M. Alter, benefits of stretching include:
enhanced physical fitness
enhanced ability to learn and perform skilled movements
increased mental and physical relaxation
enhanced development of body awareness
reduced risk of injury to joints, muscles, and tendons
reduced muscular soreness
reduced muscular tension
increased suppleness due to stimulation of the production of chemicals which lubricate connective tissues (see section Connective Tissue)
reduced severity of painful menstruation (dysmenorrhea) in females