Feb. 17, 2011 (San Diego) -- Stretching before a run won't prevent injury, but it won't cause it, either, according to a new study that has a surprising twist.
The surprise finding? Runners in the study who switched routines for the sake of research were at a higher risk of injury, says Daniel Pereles, MD, an orthopaedic surgeon in Potomac, Md.
Pereles will present the findings here Friday at the annual meeting of the American Academy of Orthopaedic Surgeons.
"If you are used to stretching, there is no reason not to stretch," he tells WebMD. "If you aren't used to stretching, there's no reason to start."
Pereles, a runner, assigned 2,729 runners who ran 10 or more miles weekly to one of two groups: a stretch group or a non-stretch group. For some, the assigned group was a continuation of their regular routine; for others, it was a switch.
Those assigned to the stretch group stretched quadriceps, hamstrings, and Achilles for 3-5 minutes just before running.
The runners had a median age of 39 (half were older, half younger). They were told to keep everything else about their routine the same for the three-month study, including any warm-up activities they did that did not include stretching (such as walking before running).
Over the course of the study, the runners reported injury, defined as any condition that prevented running for at least a week. Pereles took into account all types of injuries, including muscle tears and stress fractures.
At the end, 1,398 finished the study, including 600 assigned to the stretch group and 798 to the non-stretch group.
Overall, the injury rate in both groups was 16%, Pereles found. Among the risk factors for injury were recent or chronic injuries along with having a higher body mass index (BMI).
Runners who switched routines were more likely to be injured than those assigned to the group that continued the same habits -- stretching or not, Pereles says. Runners who stretched before the study and were assigned to the non-stretch group had a 23% increase in injuries; runners who didn't stretch before the study who were assigned to the stretch group had a 22% increase, or about a 40% increased injury risk for both groups, Pereles tells WebMD. He can't explain why.
"Your typical 5-minute pre-run stretch,” he says “doesn't make any difference in injury rate."
Jacob Wilson, PhD, of the University of Tampa, has done research on the topic and reviewed the study for WebMD. "It pretty much supports the notion that stretching is not really good for injury prevention," he says.
In his own research, he found that it's not good for enhancing performance, either. In his study, runners who stretched didn't run as fast in a half-hour performance run as those who did not stretch.
As to why the switching was associated with a higher risk of injury, Wilson can't offer an explanation either. He speculates that stretching may somehow change the running pattern, which in turn somehow boosts injury risk.
His advice for runners? "I would tell them to just warm up with the activity," such as walking before jogging.
These findings will be presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.