That's been the line of thought for many many years. It changed my freshmen year of college, when all NCAA coaches stopped doing that. The CDC did an extremely large scale study about the effects of stretching before exercise and overturned that thinking in 2004. Damn, I can't find the study itself, but google CDC 2004 and stretching and you'll find lots and lots of articles referring to it. Olympic and NCAA coaches stopped extensive pre-workout stretching then. The teams still stretch, but not nearly as much.