Stress fractures more common in underweight female runners

July 14 (UPI) -- Researchers at Ohio State University have found that female runners who are underweight are at a higher risk of stress fractures.

The study, published in the July edition of Current Orthopedic Practice, found that female Division I runners who had a body mass index, or BMI, of 19 or less were more vulnerable to stress fractures compared to runners with a higher BMI.

"We know that 20 to 25 percent of Division I athletes will have at least one stress fracture," Dr. Timothy MIller, associate professor of orthopedic surgery and sports medicine at The Ohio State University Wexner Medical Center, told UPI.

"Ours is the first study to determine how long it takes to recover from stress fractures and that it takes longer in runners with a BMI of 19 or lower. We looked at the modifiable risk factors for developing a stress fracture in these athletes."

Researchers identified 24 stress fractures in 18 patients with BMIs of 19 or below as part of a broader data base of athletes with stress fractures in the tibia over a three-year period from 2011 to 2014.

According to Miller, the study is the first in a series of five that will be coming out examining injuries in Division I athletes, there will be five studies in total.

"We were somewhat surprised by the results about BMI," Miller said. "You don't have to be thin to be fast. We don't encourage obesity, but we know a very low BMI increases the risk of getting injured. The ideal BMI for Division I athletes is between 21 and 24."

The study showed that not only was low BMI associated with a higher risk of stress fracture but that it contributed to a longer healing time in those athletes.

Miller said the reason for the increased risk of stress fracture is related to what's known as the neuromuscular hypothesis, a situation in which a person doesn't have a lot of soft tissue to dissipate the shock of running more susceptible to stress fracture.

"There's nowhere for that shock to be absorbed other than directly back into the bone. So until they build some muscle mass, put a little bit of weight back on, they're actually still at risk of developing a stress fracture later on in their career," Miller said.

He added that stress fractures are most concerning in the hip and the front of the tibia, and that any pain or soreness in those areas should be checked out by a doctor.