title: Effects of ball sports on future risk of stress fracture in runners.
abstract: OBJECTIVE
  To evaluate whether playing ball sports during childhood and adolescence is associated with the risk of stress fractures in runners later in life.
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  National track and field championships, held at Stanford University.
  
  
  METHODS
  One hundred fifty-six elite female and 118 elite male distance runners, age 18 to 44 years.
  
  
  METHODS
  A 1-page questionnaire was used to collect data regarding ages during which athletes played basketball and soccer, as well as other important covariates and outcomes.
  
  
  METHODS
  Athletes reported the ages when stress fractures occurred. Time to event was defined as the number of years from beginning competitive running to the first stress fracture or to current age, if no fracture had occurred.
  
  
  RESULTS
  In both men and women, playing ball sports in youth correlated with reduced stress fracture incidence later in life by almost half, controlling for possible confounders. In men, each additional year of playing ball sports conferred a 13% decreased incidence of stress fracture (adjusted hazard ratio [HR] and 95% confidence interval, 0.87 [0.79-0.95]. Among women with regular menses, the HR for each additional year of playing ball sports was similar: 0.87 (0.75-1.00); however, there was no effect of length of time played among women with irregular menses (HR, 1.03 [0.92-1.16]). In men, younger ages of playing ball sports conferred more protection against stress fractures (HR for each 1-year-older age at first exposure, 1.29 [1.14, 1.45]).
  
  
  CONCLUSIONS
  Runners who participate during childhood and adolescence in ball sports may develop bone with greater and more symmetrically distributed bone mass, and with enhanced protection from future stress fractures.
authors.affiliation: Department of Orthopaedic Surgery, Division of Physical Medicine and Rehabilitation, Stanford, CA 940305-5336, USA. mfred2@stanford.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Fredericson
authors.forename: Jessica
authors.initials: J
authors.lastname: Ngo
authors.forename: Kristin
authors.initials: K
authors.lastname: Cobb
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000704:Analysis of Variance; D001265:Athletic Injuries / Q000453:epidemiology* / Q000517:prevention & control; D001490:Basketball / Q000502:physiology*; D015331:Cohort Studies; D016001:Confidence Intervals; D005260:Female; D005500:Follow-Up Studies; D005538:Football / Q000502:physiology*; D015775:Fractures, Stress / Q000453:epidemiology* / Q000517:prevention & control*; D006801:Humans; D015994:Incidence; D008297:Male; D011237:Predictive Value of Tests; D011322:Primary Prevention; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D018570:Risk Assessment; D012420:Running / Q000293:injuries*; D017678:Sex Distribution; D013997:Time Factors