ABERDEEN, Md. –

Bone stress injuries, which include stress fractures, can be debilitating to athletes but are also a problem for the U.S. military, according to public health experts.

“Service members who develop BSIs may be placed on a medical profile limiting duty or training activities, or even need orthopedic surgery,” says U.S. Army Maj. Shay Lopez, a physical therapist and chief of the Defense Health Agency-Public Health Injury Prevention Branch at Aberdeen, Maryland. “By finding ways to prevent and reduce the number and severity of BSIs, the military can improve force readiness, lethality, and reduce costs.”

In pursuit of this goal, experts from the DHA-PH have been studying trends and risk factors of BSI with scientists at the U.S. Army Research Institute of Environmental Medicine and military leaders at the U.S. Army Training Center at Fort Jackson, South Carolina, an initial entry training installation for nearly half of the U.S. Army.

These scientists now have a better understanding of some factors that may increase the risk of service members’ developing a BSI.

What are bone stress injuries?

A BSI is a type of musculoskeletal overuse injury resulting from gradual, repetitive force on bone tissues. Common activities in the military that cause these injuries are running, marching, and load-bearing exercises. MSK overuse injuries continue to be a primary reason for service members’ medical visits and cost the Department of Defense billions of dollars annually. “While a gradual increase of exercise and physical activity will encourage bone and other supporting musculoskeletal tissues to strengthen over time, a BSI happens when the bone tissue doesn’t have enough time to build between activities,” says Katelyn Guerriere-Aaron, a senior research physiologist at USARIEM.

DHA-PH injury experts agree. Lopez explains that BSIs may be missed during an initial medical exam. BSIs may take time to develop, are confused with other types of injuries, or are painless until becoming severe. Catching early signs of BSIs is also difficult with motivated military personnel, who want to ‘tough out’ physical training programs for fear of restarting (known as being “recycled”) or failing military training due to injury.

“Data show most BSIs in the military are to the lower parts of the body. This includes areas extending from the hip down to the toes,” says Ryan Steelman, a DHA-PH injury prevention epidemiologist. “BSIs to the tibia, which includes a condition sometimes referred to as shin splints, are especially common among men. Women more often experience BSI to the hip or the femoral neck, an upper portion of the thigh bone.”

Diagnosing BSI injuries can be challenging, even by doctors.

“BSIs, particularly hips, can be tricky to diagnose as the pain level doesn’t always equal the severity level, and X-ray imaging doesn’t always show early BSI,” says U.S. Army Maj. Gary Helton, assistant chief of the Fort Jackson Department of Sports Medicine. “Tibial BSIs, and hip BSIs, particularly the femoral neck, can lead to a complete fracture needing surgery if not addressed in a timely manner.”

Evidence indicates extensive running and long road marches with heavy rucksacks – especially on consecutive days – are associated with military lower-body MSK injuries like these BSIs. “These training activities, however, are critical to ensuring personnel are ready for the physical rigors of combat operations,” says Steelman. “By studying BSI trends and risk factors, we are better able to help identify ways to reduce BSI impacts and build more resilient warfighters.”

Who is at risk?

New military recruits are particularly at risk of BSIs because their initial entry training, typically 10 to 16 weeks, often brings a sudden and substantial increase in the amount and intensity of their physical activity. DHA data show that while female service members have a higher risk of BSI, there are almost five times more male service members, so more men than women will develop a BSI.

“We have been diagnosing BSIs in recruits at Fort Jackson for years. A large number of these BSIs are diagnosed as early as the second and third week of training,” says Helton. “The treatment for these BSIs detracts from the success of the training.”

With support from DHA public health experts and USARIEM researchers, Helton has been able to objectively review BSI trends and risk factors and identify potential ways to reduce BSI severity and case numbers. “Many recruits who are eventually injured in training lead relatively sedentary lives prior to enlistment, so they do not have the foundation necessary for the rigors of military training,” says Helton. “Preparing their bodies with physical training before volunteering for initial military training can reduce their risk of developing a BSI during initial training programs.”

While all forms of exercise before initial military entry can improve fitness, the type of physical activity may also be important.

“Our findings suggest that specific activities that require multi-directional body movement, such as soccer or basketball, may lower rates of BSI more than exercises like running or lifting by helping build stronger overall MSK structure,” says Julie Hughes, a senior researcher and colleague of Guerriere-Aaron at USARIEM.

What risk factors can be controlled?

USARIEM experts have highlighted an especially critical finding that could help reduce the risk of BSI. “Several studies have pointed to excessive use of non-steroidal anti-inflammatory drugs, or NSAIDS, during rigorous physical training activities as a factor that will increase BSI risk,” says Guerriere-Aaron. “NSAIDS have also been found to delay healing in those who do have a bone stress injury.”

Hughes agrees that use of NSAIDs, which include products that can be purchased over the counter, such as ibuprofen, may be one of the most significant and preventable risks of BSI. “Our ongoing studies are finding that NSAIDS may increase BSI risk as much as five times during initial military entry training,” she says.

Many orthopedic doctors are aware that NSAIDs delay healing, but this may not be well known by others in the medical field, says Helton. “Since NSAIDs can be effective for pain management, many providers may prescribe NSAIDS, such as ibuprofen, for pain,” he says. “But if pain is the result of potential bone injury, research suggests NSAIDS should be avoided.”

Helton points out that recruits in military initial entry training are dependent on military medical providers for any form of medication and typically cannot purchase over-the-counter medication such as ibuprofen. “We are working to ensure military providers are aware of the NSAID risks with bone injuries. This is a key message we want to get out,” he says. “We also discourage NSAID use by recruits who may be able to access NSAIDs over the counter or from a buddy.”

Past evidence has also indicated that low bone density is a risk factor for BSI among young women who have other risk factors. Key underlying risks include poor nutrition and/or being underweight, and excessive exercise. Recent evidence suggests similar risks among young adults of both genders may contribute to low bone density and thus increase BSI risk.

Another consideration Helton observed is the added stress on recruits’ lower body bones during running or ruck march formations if drill sergeants tell recruits to ‘stride it out’, particularly shorter trainees. “There appears to be more bone stress if a trainee has to change their normal gait and stretch their legs forward to keep up with formation, landing harder on the heel and increasing stress at the hip,” Helton says. “Quicker, shorter steps may be safer, or – even better – putting shorter persons up front in a formation to manage the pace.”

What can be done by service members?

An estimated one-third of applicants to military entry training don’t meet basic military fitness standards. Recruits who are more physically fit before their initial training program have lower BSI rates. Other underlying factors, such as poor diet and lack of sleep, may make some service members more vulnerable to developing a BSI than others.

Lopez recommends that before military initial training, recruits should:

Gradually increase various exercising drills to include agility, power and balance training along with more traditional aerobic endurance (cardio) and strength exercises.
Allow time between exercise sessions for rest and bone recovery.

During training, recruits should:

Avoid NSAIDS for bone pain.
Eat nutritional foods to maintain energy levels.
Prioritize sleep to allow for bone recovery.
Avoid overreaching gaits and striding out; aim for shorter quick steps.
Seek medical assessment at the earliest signs of bone pain and follow recovery treatment plans to avoid more serious BSIs.

By reducing BSI rates and severity during initial training, the military can improve the readiness and resilience of its fighting force.