For all you weekend warriors whose athletic dreams were dashed at high school graduation, a new study might conveniently excuse the lack of power in your play. Contrary to what coach said, it turns out that stretching before you play can reduce athletic performance.

The study found that certain stretching techniques for the hamstrings and quadriceps lowered strength and power output in high-performance male and female athletes. Power was significantly reduced in those who performed the static stretches (the kind where you hold the stretch) for the typical 90 seconds. Bouncing stretches didn't significantly affect performance.

"Stretching is an important part of reducing sports injury, but the time to stretch is after performance, not before," says kinesiology professor Bill Holcomb, who also heads the UNLV Sports Injury Research Center.

So, why have gym instructors offered bad advice for so long? Picture the energy stored in your muscles like an elastic band. Static stretches before playing release some of that stored energy so there's less power to tap during the performance. If you skip the precompetition static stretch, you may not be as flexible (which can cause its own problems), but your maximum power output will improve.

"For years we've known that muscles lengthen during athletic performance; therefore, we thought that stretching before activity would prepare those muscles to lengthen and reduce injury,"says Holcomb, a longtime athletic trainer. "Studies like ours found that if you do static stretching, muscles are prepared to lengthen for injury prevention, but at the expense of force and power."

But don't forgo those warm-ups before you hop on the treadmill just yet. While the findings are significant for competitive athletes in sports that demand bursts of power, like track and football, recreational athletes are another matter. The real point is that warm-up and cool-down routines need to be customized to your activity, age, and athletic ability.

Take a children's soccer team, for example. "Range of motion is important to the sport, but normally, when the game is over, the kids have no organized cool down," says Holcomb. "If they performed basic dynamic (sport-specific) exercises during warm-up and took a few minutes to do some simple static stretches after the game, it would improve the range of motion they'll need to be both effective and injury-free when they play."

Still not sure what you should be doing? You're not alone. Though most researchers recommend sport-specific warm-ups and those holding stretches for the cool down, according to Holcomb, they don't agree on how to stretch appropriately for specific activities. Many, including other UNLV kinesiology researchers, are trying to find that perfect cocktail of static, ballistic, and dynamic stretching to both improve performance and stave off pesky injuries.