Originally Posted by DigitalRJH
Agreed. I stretch on the bike as well. You should only ever stretch a warm muscle, so after a nice warm up you can stretch on the ride. Or after you complete your ride. I stretch the upper body as well, neck stretches, low back stretches, pec and shoulder stretches. Some of those are difficult on the bike but if you are pretty proficient at no hands riding you can do them.
I stretch on my bike while riding, but that is because I get cramps in my left oblique. Not sure why that keeps happening.