BMI & Injuries

July 27, 2017

New research suggests that weighing less could come with a cost for female runners. The study’s findings show an increased risk of developing stress fractures for female runners whose body mass index (BMI) is less than 19, as well as a longer recovery time for injuries.

Researchers at the Ohio State University Wexner Medical Center conducted the study over the course of three years, using the Kaeding-Miller classification system in analyzing NCAA Division I student-athletes’ injuries. The system rates injuries from one to five—with five being the most severe—based on readings from MRIs, CT images, bone scans, X-rays, and the patient’s symptoms. 

“We found that, over time, we were able to identify factors that put female runners at an increased risk of developing a stress fracture,” Timothy Miller, MD, Assistant Professor of Clinical Orthopaedic Surgery and Sports Medicine at the Wexner Medical Center, told ScienceDaily. “One of the most important factors we identified was low bodyweight, or low [BMI].”

Along with that finding, the female student-athletes whose BMI was below 19 took about a month longer to recover from grade five stress fractures, compared to those whose BMI was 19 or above. This is significant because prior studies have suggested that 25 to 50 percent of track athletes suffer at least one stress fracture, with females having an increased incidence.

“When [BMI] is very low and muscle mass is depleted, there is nowhere for the shock of running to be absorbed other than directly into the bones,” said Dr. Miller. “Until some muscle mass is developed and BMI is optimized, runners remain at increased risk of developing a stress fracture.”

To reduce this risk, Dr. Miller suggests athletes maintain a healthy weight and incorporate strength training into their workouts.

“It’s imperative that women know their BMI and work to maintain a healthy level,” he said. “They should also include resistance training in their training regimen to strengthen the lower leg to prevent injury, even if that means adding weight from additional muscle mass.” 

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