Static stretching can weaken your workout

If you’re like most of us, you were taught the importance of warm-up exercises back in grade school, and you’ve likely continued with pretty much the same routine ever since. Science, however, has moved on. 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.

http://www.nytimes.com/2008/11/02/sp...in&oref=slogin

I've been reading about this elsewhere, I will make an effort to compile different sources of information on this soon.

What you should take away from it is that static stretching (holding your knee to your chest for 20-30 seconds, for example) before a workout is bad. Dynamic stretching (jogging around the gym or using the elliptical for 5 minutes) is better.