It makes no difference if you stretch or not before a run, because stretching won't affect your risk of injury, according to a study.
"There is a lot of controversy about this," Dr. Daniel Pereles, from George Washington University, told Reuters Health.
"Some insist you need to stretch, others say you don't, and every time I tried to assess a study on this I found that the authors were extrapolating the results from gymnasts or wrestlers or soccer players or other sprinting or short distance athletes, and nothing was related to running."
"I just wanted to know whether stretching before going for a run would be beneficial for recreational runners like myself."
Pereles and his colleagues conducted a randomized trial involving 2,729 volunteers recruited online. All were at least 13 years old and all usually ran at least 10 miles per week.
For three months, runners in one group stretched their quadriceps, hamstrings, calves and Achilles tendons for three to five minutes immediately before a run. Those in the non-stretch group ran in their usual fashion.
The runners kept all other aspects of their routine the same and self-reported any injuries, which were defined as any condition that prevented running for at least one week.
According to the study, presented this week at the 2011 annual meeting of the American Academy of Orthopedic Surgeons, injury rates were 16 percent in both groups.
The most significant risk factors for injury were a history of chronic injury or recent injury in the past four months, and a higher body mass index (a measure of body fat based on height and weight).
In addition, the runners found that starting — or abandoning — a pre-run stretching regimen was more hazardous than just sticking with a usual routine.
Runners who usually stretched and were assigned to the no-stretch group had a 40 percent increased risk of injury, while non-stretchers who were randomized to the stretch group had a 30 percent increased injury risk.
The most common injuries were groin pulls, foot and ankle injuries, and knee injuries, but there was no significant difference in injury rates between the runners who stretched and those did not for any significant injury location or diagnosis.
"It's kind of wacky — I don't really know what to make of that," Pereles said.
"You get used to your routine and if you change it, you're more likely to get injured. And the rate of injury was quite high overall, one in every six people, so running is a pretty tough sport."