title: When adolescents drop the ball: sustainability of physical activity in youth.
abstract: BACKGROUND
  A majority of youth do not attain the recommended levels of physical activity. To develop interventions that will be more efficient at enabling healthy levels of physical activity during adolescence, a better understanding is needed about which specific types of physical activity adolescents are more likely to sustain and when they tend to stop participating in each specific type of activity.
  
  
  METHODS
  From 1999 to 2005, 1276 adolescents, initially aged 12-13 years, completed a 7-day physical activity recall every 3 months during each of 5 years of secondary school. The prevalence of participation in each of 29 specific physical activities in each of Grades 7-11 was computed. Survival analyses were used to estimate when adolescents who reported each activity at baseline tended to discontinue the activity. All analyses were conducted in 2008.
  
  
  RESULTS
  The prevalence of participation in most activities declined over the 5 years; it did not increase for any activity. Within 2 years of baseline, the majority of adolescents discontinued participation in most activities in which they had reported participation at baseline. Sustained participation in a specific activity related both to its intensity (90%, 73%, and 40% of girls and 77%, 86%, and 60% of boys sustained participation in light-, moderate-, and vigorous-intensity activities, respectively) and its format (41% and 89% of girls and 69% and 90% of boys sustained participation in team and individual physical activities, respectively).
  
  
  CONCLUSIONS
  Participation in almost all physical activities declined during adolescence. The time of discontinuation varied across activity types. Promoting activities that attract and sustain secondary school students may improve physical activity levels throughout adolescence.
authors.affiliation: Centre de formation médicale du Nouveau-Brunswick, Université de Moncton, Université de Sherbrooke, and Beauséjour Research Centre, Regional Health Authority A, New Brunswick, Canada. mathieu.belanger@umoncton.ca
authors.forename: Mathieu
authors.initials: M
authors.lastname: Bélanger
authors.forename: Katherine
authors.initials: K
authors.lastname: Gray-Donald
authors.forename: Jennifer
authors.initials: J
authors.lastname: O'Loughlin
authors.forename: Gilles
authors.initials: G
authors.lastname: Paradis
authors.forename: James
authors.initials: J
authors.lastname: Hanley
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D002648:Child; D016001:Confidence Intervals; D003430:Cross-Sectional Studies; D015444:Exercise; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D010809:Physical Fitness; D015995:Prevalence; D012307:Risk Factors; D012574:Schools; D012737:Sex Factors; D013177:Sports / Q000706:statistics & numerical data*; D011795:Surveys and Questionnaires; D013997:Time Factors