Stress Fractures Are More Likely in Underweight Female Runners


Maintaining a healthy lifestyle and a healthy weight is crucial to a person’s health, but when does the healthy become unhealthy?

When a person loses too much weight, health issues can arise as well. Particularly, in female runners, it was found that a low body mass index (BMI) can lead to a higher risk of injury. The Ohio State University found that female runners classified as underweight were more likely to suffer stress fractures than those in a healthy range for BMI.

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Running is a tried and true cardiovascular and endurance exercise, and can cause weight loss in both the overweight and the healthy. Especially in long distance runners, such as cross country athletes or marathoners, it is not unusual for these people to be very thin and lean, simply due to the massive amounts of exercise they do on a daily basis. Generally, having a smaller frame means that the athlete is faster, as they do not have as much weight to carry.

The Ohio State University Wexler Medical Center examined dozens of female athletes who competed at a Division I level, meaning that they are some of the best at their sport in their age group.

Over the course of three years, the researchers used the Kaeding-Miller classification system to observe and analyze the injuries among the women. Their research shows a correlation between a low BMI of 19 or less and an increased risk of injury. Particularly, female runners with a BMI of less than 19 experience more stress fractures and take longer to heal than those with a higher BMI.

“We found that over time, we were able to identify the factors that put female runners at an increased risk of developing a stress fracture,” said assistant professor of Clinical Orthopaedic Surgery and Sports Medicine, Dr. Timothy Miller. “One of the most important factors we identified was low body weight, or low body mass index.”

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The Kaeding-Miller classification system was developed by Miller and other medical experts, and places the injury on a scale of one to five based on X-rays, bone scans, MRI images and the patient’s symptoms. The most intense stress fractures were labeled as fives, and these were the injuries most analyzed by Miller and his team. They found that among these grade five fractures, the women with a BMI of more than 19 took, on average, 13 weeks to recover. On the other hand, women with a BMI of under 19 took about 17 weeks to recover.

Stress fractures, when left untreated, can cause a sports career to end rather abruptly, as these can develop into much more painful, harmful injuries. Miller cites the importance of maintaining an injury-prevention protocol, as well as being mindful of maintaining a healthy weight. The recommended BMI for non-athletic women is 26, and athletes are encouraged to maintain a BMI of 20-24.

“It’s imperative that women know their BMI and work to maintain a healthy level. 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,” Miller said.

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