Samantha Strong knows stress fractures. A former collegiate triathlete and high school runner, the 22-year old graduate student estimates she had eight or nine over her high school and college careers. Each one, she says, took longer than the last to heal.

“My first stress fracture was in my tibia, and I was told it would take about six weeks to heal,” says Strong, who lives in Arlington. “It ended up taking two to three times that. The worst was in my femoral neck, which should have been about a three- to four-month layoff. It took six months instead.”

This comes as no surprise, says Strong, when you consider that she spent years in the grips of an eating disorder and was severely underweight. In fact, she says, “I was diagnosed with osteopenia and osteoporosis at age 16.”

Strong’s experience is consistent with the findings of a new Ohio State University study led by Timothy L. Miller. The team spent three years examining the relationship between stress fractures and time to return to running on a Division 1 team. They concluded that the lower the athlete’s body mass index (BMI), the longer the healing period.

Low weight can lead to trouble

The OSU study identified 24 tibial stress fractures in 18 women from 2011 to 2014. The researchers took into consideration the grade of the stress fractures using the K-M system. “This is a unique classification method because it considers both radiographic and clinical evidence,” Miller says. “It’s a first-of-its-kind system.”

Grade I is a stress reaction that appears only on radiographic results and doesn’t present with pain. Grade V, at the far end of the spectrum, is a nonunion stress fracture. “These are injuries that the patients have ignored or mistreated, and surgery may be needed to repair them,” Miller says. “Essentially, the body has given up trying to heal these fractures.”

In the study, the team found that the average time to return to running for those with a Grade V injury was 17 weeks, compared with 13.7 in grades II and III. The researchers also compared the women’s BMIs with those of uninjured teammates and found that the women with BMIs lower than 19 were at a higher risk to develop stress fractures .

Miller says that the likelihood for stress fractures among this population is multi-factorial. “You have to take into consideration the type of training, the amount of time the runners spent building up their mileage, as well as their BMI,” he explains. “There is still more that we need to look into and we’re dividing up a big database to do that.”

Still, Miller says that there is a pervasive problem among female collegiate runners and their perception that lighter equals faster. “Staying at a low weight may work for a while,” he says, “but eventually, it catches up to these athletes and they end up injured.”

His suggestion following his research is that these runners add lean muscle mass to support and offload the bones. “To do this, these runners may gain weight and their BMIs will go up,” he says. “But it will help keep them healthier and in the game.”

Lt. Col. Mark Cucuzzella, a professor at West Virginia University School of Medicine, says female runners with low BMIs should be aiming to add fat to their bodies. “In this age group, body fat should be in the range of 20 percent to 22 percent for hormonal health,” he says. “If it’s not there, all the calcium and vitamin D in the world won’t heal a stress fracture.”

The issue, he says, is that there are very few Division 1 female runners who hit that mark. “It’s a mismatch,” Cucuzzella says. “Many of these women will show up at college with delayed puberty because they stay low weight in hopes of better performance. In the end, however, they break.”

This was very much Strong’s story. “It took three or four stress fractures before anyone really brought it up to me,” she says, “and all along, I was under-fueling and underweight. I didn’t get a period the entire time.”

Cucuzzella says that for women who haven’t built up the proper bone density by age 20, a lifetime of fractures may await. “Coaches, physicians and athletic trainers all need to tell this population that it’s okay to add fat and that if they don’t, they’re not going to get healthy.”

Although Strong admits she is never far from the urges to control her eating and stay at a low weight, she is in a much better place than just a few years ago. “Since getting it out in the open and working with a nutritionist, I’ve had a growth spurt,” she says. “I put on about 15 pounds and grew two inches once I started eating.”

Even better: She now finds joy in running and is able to maintain about 50 miles per week without injury. “I haven’t had a stress fracture in a full year,” she says. “It’s exciting to be here.”