For the most part, the video shows evidence thats been around for over a decade or more and is not necessarily popular knowledge. This video, however, is hardly a comprehensive review on the role flexibility training has on overall athletic performance (even in cycling). The video limits its focus on stretching with regard to:
- pre-cycling stretching and performance
- post-workout muscle soreness; which unless your completely inexperienced or out of shape for the first few weeks of a return to training has little to do with the low-impact, concentric-only nature of cycling.
- injury prevention: acute injury ok; chronic injuries, see low back pain on next point
- low back flexibility/pain and aggressive cycling position (notice how he kind of danced around hamstring flexibility, which is the actual the limiter of our positions and more behind the cause for Low Back Pain rather that low back extensor flexibility)
For that last point flexibility training is important, particularly in the hamstrings for cyclists if you want/have a more aggressive position and/or have LBP on or off the bike. Also, hip flexors can get very tight in cyclists (particularly the psoas), which in conjunction with "loose" hamstrings causing an imbalanced pelvis, can lead to low back pain. A balanced hip-down flexibility routine can in fact help that problem.
Indeed, most if not all of what he says is pretty much true, but listen to the circumstances he is offering. They are very specific. The title of the video was obviously made to get people to watch it, and it does control the facts and statistics to show what he's trying to say, but it lacks the comprehension to provide a full picture with relation to your title "stretching not useful". He doesn't ever go over how to actually improve position, have more aggressive position, prevent back pain, etc., and mentions yoga as an afterthought and could have elaborated also on the counterpoints of possible benefits of other types of flexibility training or even eccentric weight training (a whole 'nother can of worms, but does has influences on flexibility).
The most important thing he said in the whole video was at the very end:
"If you enjoy stretching, do it. If you don't enjoy stretching, then don't do it.
As long as you're not stretching right before you ride, it'll probably have very little effect on your cycling [performance that day]."
I, personally, would still recommend even a light flexibility routine as a separate exercise routine. It may not help your cycling if you do it right before, but as a separate workout it will only help for the other 20-23 hours of the day you're not on the bike, and may even improve life on the bike anyway.
Matt Leu, M.S. Kinesiology
San Pedro Fit Works, Los Angeles, CA
Endurance Athlete and Coach
Consistency/time=results