A controversy about whether one should stretch before or after running, or not at all, has some new ammunition; it's possible that stretching can neither prevent nor cause injury.

A study presented Thursday at the annual meeting of the American Academy of Orthopedic Surgeons in San Diego, concludes that injuries were more likely depending on the the number of miles run, the heavier and older the runner, recent or chronic injury and switching pre-run stretching routines.

Risk for injury is related to age, weight and distance run. (Joe Brandt, iStock)

More than 70 million people worldwide run recreationally or competitively and there's been much debate about stretching before hitting the pavement.

Dr. Daniel Pereles, an orthopedic surgeon from the Washington, D.C. area, and a runner himself, divided 2,729 runners who run 16 or more kilometres per week into two groups, those who stretched and those who didn't .

Runners in the stretch group stretched their quadriceps, hamstrings, and gastrocnemius/soleus muscle groups. Their routine took three to five minutes and took place immediately before running. The two groups were monitored for three months.

Some runners in the two groups were randomly chosen to either start stretching or to stop stretching for the study.

"Although all runners switching routines were more likely to experience an injury than those who did not switch, the group that stopped stretching had more reported injuries, implying that an immediate shift in a regimen may be more important than the regimen itself," noted Pereles.

The study recommends that those who typically stretch now before a run should continue to do so or risk injury.

The most common injuries sustained were groin pulls, foot/ankle injuries, and knee injuries.