High-impact sports linked with higher risk of stress fracture among adolescent girls

Adolescent girls participating in high-impact physical activities may have an increased risk of developing stress fractures, according to a study published online in the Archives of Pediatrics & Adolescent Medicine.

“Weight-bearing activity stimulated bone remodeling and thus increases bone mass density, but very high levels of activity may be detrimental to bone health and increase the risk of stress fracture,” Alison E. Field, ScD, and colleagues wrote. “Although stress fractures are relatively uncommon, they affect as many as 20% of young female athletes and military recruits.”

The researchers performed a prospective cohort study that included 6,831 girls aged 9 to 15 years old. Participants were daughters of women enrolled in the Nurses’ Health Study II, according to a press release.

Data collection and findings

Self-reported questionnaires were used to collect data each year from 1996 to 2003, with the exception of 2002. The girls’ history of stress fracture, including the fracture location and the girl’s age at the time of fracture, were reported by their mothers in 2004. The incidence of stress fracture occurring between 1997 and 2004 was the main outcome measure for the study.

According to the release, researchers found that 267 girls (3.9%) developed a stress fracture during the 7-year follow-up. Family history of osteoporosis or low bone mass density was strongly associated with the risk of stress fracture, as girls who had such a family history were almost twice as likely to develop a stress fracture.

With regards to activity, girls who engaged in 8 or more hours of physical activity per week were twice as likely to develop stress fracture compared with those who engaged in less than 4 hours of activity per week. The study found an independent association between an increased risk of stress fracture and participation in basketball, running, and gymnastics/cheerleading.

“Our study observed that high-impact activities — specifically basketball, running and gymnastics/cheerleading — significantly increase risk for stress fracture among adolescent girls,” the authors wrote. “Thus, there is a need to establish training programs that are rigorous and competitive but include varied training in lower-impact activities to decrease the cumulative amount of impact in order to reduce the risk of stress fracture.”

Other predictive factors

The study also noted that non-impact and medium-impact activity were not predictive of increased risk of stress fracture, adding that each hour of high-impact activity was found to increase that risk by 8%.

Risk of stress fracture was also increased by an older age at the start of menstrual cycles, as each 1-year delay in onset of menstruation was associated with an approximately 30% increase in risk. Being underweight, overweight, or engaging in disordered eating were not found to be associated with the risk of developing a stress fracture.

“Clinicians, parents and coaches should continue to promote activity to young girls but should make sure that training hours are not excessive, thereby not compromising bone health,” the authors concluded.

Reference:
Field AE, et al. Prospective study of physical activity and risk of developing a stress fracture among preadolescent and adolescent girls. Arch Pediatr Adolesc Med. 2011; April 4. [E-pub ahead of print]. doi:10.1001/archpediatrics.2011.34
Disclosure: No relevant financial disclosures were reported.

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