Running a risk

And if she has a low body mass index, or BMI, her injury risk is even higher, according to a recent study led by Dr. Timothy Miller, an orthopedist with The Ohio State University Wexner Medical Center.

Miller led a team that analyzed injuries among young female runners for three years. Specifically, the team examined young women, many of whom had tibial stress fractures — that is, stress fractures of the larger of the two bones in the lower half of the leg — who were Division 1 college athletes.

Study results were published in the journal Current Orthopaedic Practice.

You may not be a young female runner on a Division 1 track team. Most of us aren’t. But if you’re an athlete who likes to pound the pavement, having a lower body mass can be a little risky.

Stress fractures are a very common sports-related injury, according to the American Academy of Orthopaedic Surgeons. Miller noted that 25 to 50 percent of track athletes develop at least one stress fracture in their career — and female athletes experience an increased incidence.

Having a BMI of 19 or lower puts you at higher risk for developing stress fractures, too. A stress fracture is essentially an overuse injury. It’s a small crack or bruise within a bone. The bones of your foot and lower leg are the most vulnerable to developing stress fractures because they absorb the stress of walking, jumping and other weight-bearing activities.

Stress fractures tend to develop when you increase the duration or intensity of your running (or other type of weight-bearing exercise) too much or too quickly.

So, if you’re a woman with a relatively low BMI and a tendency to overdo it out of impatience or enthusiasm, try to dial it down a bit. Try limiting your mileage or alternating runs with some other low-impact activity, such as swimming or cycling. Alternately, you could build up your muscle mass and put on a little weight, which also can help.

Miller suggests that female runners maintain a BMI between 20 and 24, incorporating strength training, resistance training and other low-impact activities into their workout regimen. (Older women especially should be deliberate about this because women tend to lose more bone mass as they age, and they’re at a higher risk for developing conditions like osteoporosis.)

Your shinbones (and maybe a few other bones, too) will thank you.

BMI at a glance

Body mass index is a measurement of your body fat that takes into account your height and weight. What’s a normal BMI? According to the Centers for Disease Control and Prevention (CDC), the average BMI for a woman is 26.

What’s your BMI and what does it say about you? Check out the BMI categories, according to the National Heart Lung and Blood Institute:

• Underweight: Below 18.5
• Normal weight = 18.5–24.9
• Overweight = 25–29.9
• Obesity = BMI of 30 or greater

Prevent a stress fracture

The best way to address a stress fracture is to prevent it from occurring in the first place. The American Academy of Orthopaedic Surgeons recommends these strategies:

Wear the right shoes. Make sure you’re wearing athletic shoes that fit properly and aren’t worn out. Old shoes lose their ability to absorb shock.

Ramp up gradually. Start slow and build from there. A good rule of thumb is to limit your increase in time, speed or distance to 10 percent per week.

Cross-train. You love to run, but your body needs other activities, too. Mix it up by biking or swimming in between your runs.

Build up your strength. As you age, you lose bone density. Build up your bones and your muscles by adding some strength-training exercise to your routine.

Eat right. Make sure you get plenty of calcium and Vitamin D in your diet to keep your bones strong. While supplements may be a good option if you’re not getting enough vitamins in your diet, sports medicine doctors at Wexner Medical Center recommend meeting with a registered dietician before taking supplements.