title: Influence of multiple risk behaviors on physical activity-related injuries in adolescents.
abstract: OBJECTIVE
  The study objectives were to (1) examine the relationship between physical activity and physical activity injuries in youth, (2) determine whether this relationship is modified by the engagement in multiple risk behaviors, and (3) determine whether this relationship is modified by the setting of the injury (school versus outside of school).
  
  
  METHODS
  We examined associations between physical activity and multiple risk behaviors with physical activity injuries occurring at and outside of school. The study population consisted of a representative sample of 5559 Canadian youth in grades 6 through 10 who participated in the 2001/2002 Health Behavior in School-Aged Children Survey. The exposure and outcome measures were determined from a classroom-based survey.
  
  
  RESULTS
  Irrespective of grade, there were strong gradient relations between physical activity participation and related injuries outside of school. Conversely, there were modest relations between physical activity participation and related injuries at school. In students in grades 6 to 8, there was no relation between multiple risk behaviors and physical activity injuries at school and a curvilinear relation between multiple risk behaviors and physical activity injuries outside of school. The opposite pattern of relationships between multiple risk behaviors and injuries was observed in students in grades 9 to 10. Irrespective of grade and setting of injury, there was no significant interaction between physical activity and multiple risk behaviors on injury risk. The results were consistent by severity of injury and for structured/organized and unstructured/informal forms of physical activity.
  
  
  CONCLUSIONS
  The environment moderated the relation between physical activity and related injuries in that strong risk gradients only existed outside of the school setting. Unexpectedly, there were no consistent gradients between the engagement in multiple risk behaviors and physical activity injuries or any interaction effect between physical activity exposure and multiple risk behaviors. These findings suggest that optimizing the environment would be a preferred strategy for preventing physical activity injuries compared with selectively targeting youth who engage in multiple risk behaviors.
authors.affiliation: Department of Community Health and Epidemiology and School of Kinesiology and Health Studies, Queen's University, 69 Union St, Kingston, Ontario, Canada K7L 3N6. janssen@post.queensu.ca
authors.forename: Ian
authors.initials: I
authors.lastname: Janssen
authors.forename: Suzanne
authors.initials: S
authors.lastname: Dostaler
authors.forename: William F
authors.initials: WF
authors.lastname: Boyce
authors.forename: William
authors.initials: W
authors.lastname: Pickett
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D017677:Age Distribution; D001265:Athletic Injuries / Q000453:epidemiology*; D002170:Canada / Q000453:epidemiology; D015984:Causality; D003430:Cross-Sectional Studies; D005260:Female; D006306:Health Surveys; D006801:Humans; D008019:Life Style; D008297:Male; D016017:Odds Ratio; D015995:Prevalence; D012044:Regression Analysis; D012309:Risk-Taking; D012574:Schools / Q000706:statistics & numerical data