By Dev K. Mishra, M.D.
President, Sideline Sports Doc
Clinical Assistant Professor of Orthopedic Surgery, Stanford University
A stress fracture is an overuse injury that occurs when muscles become fatigued and eventually are unable to absorb the shock from a sport or fitness activity. Rather than being absorbed by the muscle, the stresses are instead transferred to the bone causing an injury to the bone itself. The bone injury is called a stress fracture.
Stress fractures in adolescent athletes are unfortunately fairly common. Here’s an interesting recently published scientific study that aims to identify risk factors for stress fractures in adolescent athletes. The authors found several characteristics associated with stress fracture risk: lower than normal body mass index, four weeks or more history of shin splints, minimal involvement in weight training, decreased amount of sleep, daily stress, and low dairy intake.
Data was collected from the National High School Stress Fracture Registry (NHSSFR), an internet-based adolescent stress fracture database. These findings were compared with a survey of 100 healthy athletic controls to identify significant differences between healthy adolescents and those with bone stress injury. Due to the design of the study, it did not identify cause and effect but instead sought to find an association between certain characteristics and stress fractures.
Taken as a whole these are interesting findings and there are a few messages that we can take away from the data.
First, a lower than normal body mass index may be a sign of reduced energy availability, similar to what takes place in the female athlete triad. While there are plenty of athletes with lower than normal body mass index who will never develop a stress fracture it is still reasonable and plausible to make an association between low body max index and less than optimal nutritional health.
Inclusion of resistance training exercises in any athlete’s training regimen should be beneficial. Resistance training improves muscle strength, power, and tendon resiliency, all of which will help to reduce stress on the bone.
Lower than normal dairy intake may have an effect on calcium intake, vitamin D metabolism, and also have a negative effect on bone health. This would also contribute to stress fracture risk.
I’m not sure what to make of the association with increased daily stress and reduced amounts of sleep. Connecting the dots between those aspects of health and development of a bone stress injury would be speculative.
This study aims to find factors associated with bone stress injury in adolescents and is commendable for being one of the first studies to do so. Further research is needed to prove cause and effect.
We come back to many of the principles that I’ve written about previously: young athletes should participate in multiple sports and cross train to the extent possible. Try to limit single sport participation to eight months or less out of the year. Do resistance training exercises, and optimize nutritional intake.