For Dr. [Stephen] Thacker's paper "The Impact of Stretching on Sports Injury Risk: A Systematic Review of the Literature," he and his colleagues pored over nearly 100 other published medical studies on the subject. Their key conclusions: stretching does increase flexibility; the highest-quality studies indicate that this increased flexibility doesn't prevent injuries; few athletes need extreme flexibility to perform their best (perhaps just gymnasts and figure skaters); and more injuries would be prevented by better warmups, by strength training, and by balance exercises, than by stretching.
Ian Shrier, M.D., a past president of the Canadian Society of Sports Medicine, has been drilling into the stretching literature since the early 1990s. In a 1999 paper titled "Stretching Before Exercise Does Not Reduce the Risk of Local Muscle Injury," Dr. Shrier lists five reasons why stretching shouldn't be expected to work. Among them: stretching won't change eccentric muscle activity (when a muscle simultaneously contracts and lengthens, as in downhill running), which is believed to cause most injuries; stretching can produce damage at the skeletal level; and stretching appears to mask muscle pain, which could cause the exerciser to ignore this key pre-injury signal. He concludes: "The basic science and clinical evidence today suggests that stretching before exercise is more likely to cause injury than to prevent it." ...
The best research on stretching and injury prevention has been done with military recruits. Military training has much in common with exercise, and the Army has a huge interest in keeping injuries to a minimum. In one study, titled "Physical Training and Exercise-Related Injuries," a U.S. Army research team found that trainees with the highest and lowest flexibility had the highest injury rates. They were, respectively, 2.2- and 2.5-times more likely to incur an injury than trainees with average flexibility. Apparently, when it comes to flexibility and injuries, don't try to be all that you can be. Settle for average.
--Amby Burfoot, Runner's World, on more evidence against conventional fitness wisdom