I liked this discussion from cyclingnews.com by Scott Saifer, and not just because I have been coached by Scott - I think his approach is pretty good, and he's funny:

____________

Stretching

I'm an 18 year old recreational rider who is doing 2 hour rides a few times a week. I'm not a very limber person and I usually do only two or three very basic stretches before and after my rides. I'm constantly sore and I think i'm missing some key stretches. What are the essential stretches every cyclist should do before and after a ride?

Will Pollock

Scott Saifer replies:

A few years ago I read a self-help/philosophy sort of book that suggested the introduction of a new word that would mean something between "yes" and "no" which was definite, not "maybe". The proposed new word was "po". You've asked a po sort of question here. There are no "key stretches every cyclist should do". The goal of stretching, if it is needed, is to develop the functional flexibility to efficiently and comfortably ride the bike. A rider who can already do that does not need to stretch. A rider who cannot pedal smoothly and comfortably should first get a good bike fitting to maximize performance with the current level of flexibility, and should then work on the specific elements of flexibility that continue to interfere with riding, or that seem likely to enhance performance, such as stretches that allow the rider to get lower or narrower, or to bring the knees closer to the top tube.

Here's another perspective :

Dave Fleckenstein replies:

I would take a slightly different approach to Scott, mainly due to the fact that I deal not as much with the healthy cyclists, but those who have become injured. Anytime that the body is subjected to repetitive activity, there is accumulation of breakdown and postural adaptation. If the body is constantly accumulating a pattern and not consistently perfoming maintenance to offset the repetive activity, than negative changes occur. In the case of cyclists, I tend to see excessive mobility present in the lumbar spine (accelerating the likelihood of degenerative changes) due to prolonged lumbar flexion, weak stabilization musculature, and tight lower extremity musculature (which limits normal motion of the pelvis and lumbar spine). I highly recommend my athletes perform fairly regular hamstring, hip flexor, and hip musculature (particularly piriformis and iliotibial band) stretching.

I would caution that there are many wrong ways to stretch and few right ways - I am making a more detailed program for CN this fall. I regularly have clients who mistakenly think that bending forward to touch the toes equates to hamstring stretching, when it reality it more closely correlates to stretching the lumbar spine - not a good thing to do consistently. I participate (cautiously) in yoga, and watch people trying to strain and struggle in poses (such as downward dog) and, rather than swallow their pride and use props or stretch less to maintain a strong neutral spine, they end up creating local stresses on the spine and are ultimately doing more harm than good.

Finally, as I live in a town that has a formula driven fit program that in my opinion creates more pathology than performs improvement, I would urge caution at being fit without first assessing normal mobility. The bike fit should be adapted to your current body and the mistake that most bike fit "pros" make is that the body will somehow adapt to an aggressive position. I can tell you absolutely it will not. If you are fit to an aggressive position without having adequate flexibility, the hamstrings do not lengthen, the lumbar spine does so preferentially, making support structures such as the disc and ligaments excessively lax. This leads to accelerated breakdown of the lumbar spine. Bike fitting is a constantly evolving project.. If I have a higher level racer who requires a more aggressive position, I will assess the ability of the racer to attain that position, prescribe a flexibility and stabilization program to enable them to succeed in that position, and slowly bring them to the desired position.