In Stretching: The Truth, the New York Times finally gets around to sharing a basic fitness fact — stretching is not the same as warming up:
Researchers now believe that some of the more entrenched elements of many athletes’ warm-up regimens are not only a waste of time but actually bad for you. The old presumption that holding a stretch for 20 to 30 seconds — known as static stretching — primes muscles for a workout is dead wrong. It actually weakens them. In a recent study conducted at the University of Nevada, Las Vegas, athletes generated less force from their leg muscles after static stretching than they did after not stretching at all. Other studies have found that this stretching decreases muscle strength by as much as 30 percent. Also, stretching one leg’s muscles can reduce strength in the other leg as well, probably because the central nervous system rebels against the movements.
Instead, modern experts recommend dynamic stretches — which, years ago, we were all told were dangerous. Sigh.