You can always add more power...

...if you don't mind the occasional broken bone or pulled muscle! It's true, there are athletes who treat their bodies like race cars, thinking they just need to increase power and reduce weight to get optimum results. While those are two factors to be concerned with, cycling (and many other sports) requires a certain amount of neuromuscular timing to get the job done. All this means is that all cylinders need to be firing at their respective optimums to produce peak output. (Did you catch that? For some reason I'm trying to appeal to the motorheads.) If you are using four muscles for a movement, but one is a bit tight, it will decrease the effectiveness of the others. Well toned muscles require less energy to move through their range of motion. For example, riding a bike with a rusty chain may get you where you want to go, but you're doing more work. Why not just oil the chain? With muscles and other soft tissues, this is done by increasing circulation. Massage and proper stretching facilitate increased circulation, as well as increased range of motion.

There are a few studies claiming that stretching decreases power. First of all they overuse a poor form of stretching (holding stretches for an excessive and arbitrary length of time, and secondly, they do it immediately before testing the muscle for power. There is no time allowed for reinnervation! Taking these errors into consideration, I would also guess most of the studies focus on classically overstretched tissue as opposed to lengthening the contracted tissue. But enough of that. Do your own study; let me show you how easing tension in the right spots can help your performance in whatever sport you choose.