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Stress Fractures in Young Runners: Identifying Risk Factors

Stress fractures are highly common among high school runners.  Like many conditions, certain risk factors emerge to help predict this entirely preventable injury.  Let’s face it, if you run so far and so hard that you break your own bones you’ve probably missed a LOT of risk factors.  But with college scholarships on the line, it’s not surprising that injuries will sometimes occur.  Understanding risk factors can help coaches and athletes navigate that very fine line between injury and optimal performance.      

One recent study on high school running stress fractures (Tenforde (2013)) surveyed 748 competitive high school runners (442 girls and 306 boys) and tracked the subjects for an average of 2.3 seasons of cross country and track.  428 girls and 273 boys provided follow up responses.  Authors noted the following that tibial (shin) stress fracture was most common in females and foot stress fractures were most common in males. 

Most significant risk factors for fractures in girls included

  • prior fracture
  • low BMI ( less than 19)
  • late menarche (15 years or later)
  • previous participation in gymnastics or dance

For boys prior fracture and increased number of seasons were associated with an increased rate of stress fractures, whereas prior participation in basketball was associated with a decreased risk of stress fractures.

It is always unfortunate to see the prior injury robustly predicts future injury.  If someone gets hurt you already know they are at risk; if they get hurt again it means they got hurt when you were already on notice of their increased risk!    

The finding that increased seasons were correlated with increased risk with boys also stands out.  Essentially, boys get more broken down the longer they stay with the sport.  Rather than building on their base, they gradually get run into the ground! 

Basketball participation was protective for boys but gymnastics and dance increase risk for girls.  These findings would indicate that moderate amounts of jumping and sprinting are good but too much is bad.  As a broad generalization, most would agree that training volumes are lower in basketball compared to gymnastics and dance, which can push the limits of training volume even at the younger levels. 

Another recent study (Yagi 2013) also looked at risk factors in high school runners for medial tibial stress syndrome and stress fractures.  Authors studied 230 runners and followed up three years later.  Variables tested as risk factors included height, weight, body mass index (BMI), range of hip and ankle motion, straight leg raising (SLR), intercondylar and intermalleolar interval, Q-angle, navicular drop test, hip abductor strength and physical conditioning.

Authors noted BMI, internal hip rotation angle were most predictive of stress fractures in females.  Limited straight leg raise most correlated for stress fractures in males.

Although prospective studies are often desirable, looking backward can also offer insight when considering elite athletes.  Fredericson (2005) surveyed 156 female and 118 male elite runners ages 18 to 44 and focused on prior sport participation, much like Tenforde (2013).

In both men and women, playing ball sports in youth correlated with reduced stress fracture incidence later in life by almost half.  In men, each additional year of playing ball sports conferred a 13% decreased incidence of stress fracture.  Playing ball sports at a younger age also was associated with decreased risk.  Among women with regular menses, participation in ball sports also was correlated with reduced stress fractures, but not among women with irregular menses. 

Conclusion

The research is clear that coaches do a poor job protecting those most at risk, as prior stress fracture consistently predicts future stress fracture.  If coaches and athletes learned their lessons from prior mistakes, this correlation between previous injury and future injury would not exist.  If you use the information correctly, past injury should actually improve injury resistance because it gives you warning about who is at risk. 

On a positive note, the evidence does support that playing other sports such as basketball can improve stress fracture resistance in young runners.  One theory is that varied movement skills found on the basketball court can help develop the resilience needed to better withstand injury during distance running.  Kids with a better movement vocabulary are simply more resistant to injury than those who specialize early.  Another explanation is that varied sports spare runners from inevitable pounding. 

Stress fractures are entirely preventable if you train intelligently and understand the risk factors.  Though this injury is more commonly associated with young female runners, male runners also deserve careful attention to prevent this injury. 

References

Fredericson M, Ngo J, Cobb K.  Effects of ball sports on future risk of stress fracture in runners.  Clin J Sport Med. 2005 May;15(3):136-41.

Yagi S, Muneta T, Sekiya I.  Incidence and risk factors for medial tibial stress syndrome and tibial stress fracture in high school runners.  Knee Surg Sports Traumatol Arthrosc. 2013 Mar;21(3):556-63. doi: 10.1007/s00167-012-2160-x. Epub 2012 Aug 9.

Tenforde AS, Sayres LC, Liz McCurdy M, Sainani KL, Fredericson M. Identifying Sex-Specific Risk Factors for Stress Fractures in Adolescent Runners.  Med Sci Sports Exerc. 2013 Apr 11. [Epub ahead of print]

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