Female runners with a low body weight are more likely to have stress fractures and take longer to recover from them, according to a new study.
Researchers from the Ohio State University Wexner Medical Center reviewed data on dozens of injuries suffered by female college runners. They found that runners with a body mass index (BMI) below 19 were more likely to suffer stress fractures than others. BMI is an estimate of body fat based on weight and height.
Women with a low body weight were also sidelined longer after an injury. Among those with the most severe stress fractures, recovery time was 13 weeks for women with a BMI of 19 or higher. That compared to more than 17 weeks for those with a BMI below 19, the study found.
“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 study co-author Dr. Timothy Miller, assistant professor of clinical orthopedic surgery and sports medicine.
“One of the most important factors we identified was low body weight, or low body mass index,” he said in a hospital news release.
Having too little lean muscle mass to dissipate the impact of repetitive pounding on hard surfaces makes the bones of runners’ legs vulnerable to injury, according to Miller.
“When body mass index 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. Until some muscle mass is developed and BMI is optimized, runners remain at increased risk of developing a stress fracture,” he explained.
Female athletes should maintain a BMI of 20 to 24, Miller suggested.
A woman who is 5 feet, 5 inches tall and weighs 120 pounds has a BMI of 20, according to the U.S. Centers for Disease Control and Prevention.
The BMI for an average American woman is 26, the CDC says.
To prevent injury, Miller said women should stay at a healthy BMI and include resistance training in their workout regimen to strengthen their lower legs, “even if that means adding weight from additional muscle mass.”
The study was published recently in the journal Current Orthopaedic Practice.
Whether you’re an avid basketball player or a weekend hiker, you may be at risk for a stress fracture if you overdo it.
A stress fracture occurs when you increase the length or intensity of your workout too quickly. Your muscles become so tired by the extra work that they transfer the stress to the bones — most often in the lower leg — and a tiny crack appears. A stress fracture can also happen when you workout on a different surface or use the wrong equipment for you, says the American Academy of Orthopaedic Surgeons (AAOS).
With proper rest, your bones have the time they need to repair any tiny fractures or grow stronger so they can take the wear and tear of an activity.
Doing too much too soon is a big mistake. In other words, it’s very important to have realistic expectations for your body.
Be sure to check with your healthcare provider before beginning a fitness program. Once you get the OK, don’t try to run 10 miles or join a football team if channel surfing has been your main activity for years. Start out slowly, and increase your level of activity gradually.
Building up slowly is also important to let your bones get used to the type of surface where you exercise. If you walk or run, for instance, start on flat and soft surfaces. Dirt paths tend to be better than asphalt, and asphalt can be better than concrete.
Invest in athletic shoes that provide good cushioning and support for the arches of your feet. Replace your shoes when they show signs of wear. Try to shop at stores that can offer guidance for your specific needs. Alternating your exercise program, or cross training with low impact activities can reduce the risk of a stress fracture.
Women seem to develop stress fractures more often than men, the AAOS says. That may be because women are more likely to have eating disorders and osteoporosis. As a woman’s bone mass reduces, the chances of getting a stress fracture increase. Make sure your diet provides enough calcium and vitamin D for strong bones.
If you’re in pain the minute you start walking or running and the pain doesn’t quiet down when you stop or after icing, it’s time to get help. Your healthcare provider can come up with a diagnosis and treatment to put you back on track. The most important treatment is rest. Most stress fractures take 2 to 4 weeks to heal with reduced activity and protective footwear. In some instances, certain bones may take up to 8 weeks to heal, depending on your situation.