title: Prospective study of physical activity and risk of developing a stress fracture among preadolescent and adolescent girls.
abstract: OBJECTIVE
  To identify predictors of developing a stress fracture among adolescent girls during a 7-year period.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Adolescent girls living throughout the United States.
  
  
  METHODS
  A total of 6831 girls aged 9 to 15 years at baseline in the Growing Up Today Study, an ongoing prospective cohort study.
  
  
  METHODS
  Exposures were assessed by self-report questionnaires completed by adolescent girls in 1996, 1997, 1998, 1999, 2000, 2001, and 2003. The adolescent girls' history of stress fracture, including age when fracture occurred and site, were reported by their mothers, who are registered nurses, in 2004. Cox proportional hazards models were used in the analysis. Main Outcome Measure Incident stress fracture that occurred between 1997 and 2004.
  
  
  RESULTS
  During 7 years of follow-up, 267 girls (3.9%) developed a stress fracture. Independent of age, age at menarche, family history of fracture, and hours per week of low- and moderate-impact activity, hours per week of running (hazard ratio = 1.13; 95% confidence interval, 1.04-1.23), basketball (hazard ratio = 1.12; 95% confidence interval, 1.03-1.23), and cheerleading/gymnastics (hazard ratio = 1.12; 95% confidence interval, 1.02-1.22) were significant predictors of developing a stress fracture. No other type of high-impact activity was associated with an increased risk.
  
  
  CONCLUSIONS
  Girls who engage in running, basketball, cheerleading, or gymnastics should be encouraged to include varied training in lower-impact activities to decrease the cumulative amount of impact in order to minimize their risk of stress fractures.
authors.affiliation: Division of Adolescent/Young Adult Medicine, Children's Hospital Boston, 300 Longwood Avenue, Boston, MA 02115. USA. alison.field@childrens.harvard.edu
authors.forename: Alison E
authors.initials: AE
authors.lastname: Field
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Gordon
authors.forename: Laura M
authors.initials: LM
authors.lastname: Pierce
authors.forename: Arun
authors.initials: A
authors.lastname: Ramappa
authors.forename: Mininder S
authors.initials: MS
authors.lastname: Kocher
mesh_terms: D000293:Adolescent; D001265:Athletic Injuries / Q000453:epidemiology*; D015519:Bone Density; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D015775:Fractures, Stress / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D008572:Menarche; D010024:Osteoporosis / Q000453:epidemiology; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012306:Risk; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology