JAMA Logo Weight-bearing activity is believed to stimulate bone remodeling and thus elevate bone mass density. Well, very high levels of activity may be detrimental to bone health and increase the risk of stress fracture. A latest study claims that adolescent girls participating in high-impact physical activity, especially basketball, running and gymnastics / cheerleading, are at heightened chances of developing stress fractures.

This conclusion was drawn after evaluating data on 6,831 girls between the ages of 9 and 15. The study subjects were daughters of women enrolled in the Nurses’ Health Study II and data was gathered through self-report questionnaires completed between 1996 and 2004. In the seven years of follow-up, 3.9 percent forming 267 girls were supposedly diagnosed with a stress fracture. Family history of osteoporosis or low bone mass density was apparently linked with the threat of stress fracture.

Authors explain, “Our study observed that high impact activities, specifically basketball, running and gymnastics/cheerleading, significantly increase risk for stress fracture among adolescent girls. 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. Therefore, 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.”

Investigators found that girls with a family history of osteoporosis or low bone mass density had an almost two-fold higher risk of stress fracture. Participants who engaged in eight or more hours of physical activity a week probably were twice more likely to develop a stress fracture than those spending less than four hours of activity per week. Alison E. Field, Sc.D., of Brigham and Women’s Hospital and Harvard Medical School, Boston, and colleagues also examined high-impact sports individually. Basketball, running and gymnastics/cheerleading appeared independently associated with increased risk of stress fracture.

This risk may not be predicted well in advance by non-impact activity or medium-impact activity. However, each hour of high-impact activity presumably elevated the chances of experiencing stress fractures by almost 8 percent. Experts also observed that older age at the start of a girl’s menstrual period raised the chances of developing stress fracture. Each one-year delay in onset of menstruation was reportedly linked with an approximate 30 percent increase in risk. It was mentioned that being underweight, overweight and engaging in disordered eating apparently fails to interfere with the threat of being diagnosed with stress fracture.

The study will appear in the August print issue of Archives of Pediatrics and Adolescent Medicine, one of the JAMA/Archives journals.