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Stretching Before Exercising Weakens Muscles
Khemisty writes "Back in grade school you were probably taught the importance of warm-up exercises, and it's likely you've 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 are 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, 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."
The "stretching reduces injury" canard has been disproven in study after study. Warming up may have some benefit, but stretching isn't the way to go if you're worried about injuries.
One study is at http://www.sportsinjurybulletin.com/archive/stretching-exercises.html
As it turned out, stretching during warm-up had no statistically significant effect on the risk of injury, either for soft-tissue problems or bony disorders...Although pre-exercise stretching was totally unimportant from an injury standpoint, other easy-to-determine factors actually did a decent job of prognosticating who would get hurt. For example, age was a good predictor of injury (the older the athlete, the higher the injury frequency)...In addition, 20-metre shuttle-run time was an outstanding predictor (the faster the time, the lower the risk of injury), a relationship which suggested that overall fitness -- not the presence or absence of pre-workout stretching -- had the paramount influence on injury occurrence
rage, rage against the dying of the light
As a martial artist, I now only do dynamic stretches before practice or sparring. I stopped doing *static* stretches before I spar or work out because it made me slower. My stretching coach told me the same - do the splits and stuff afterward, and do range of motion stuff (like doing light stretch kicks until you build up to your maximum range) beforehand. This is also very important in Judo, where any leg stretches you do beforehand may make your footwork slower and hence make it easier to be thrown. Dynamic stretches also have the advantage of not slowing down your heart rate before your big event.