title: The decline in physical activity among adolescent students: a cross-national comparison.
abstract: BACKGROUND
  The decline in physical activity during adolescence is a key public health concern. This comparative study assesses whether the age-related decline in physical activity among high school students occurs similarly in the United States (U.S.) and Ontario, whether the decline in physical activity is steady throughout the age range, or whether any declines are age-specific.
  
  
  METHODS
  Data are based on self-reports of 9th- to 12th-graders derived from the 2001 Youth Risk Behavior Survey (n=13,503) and the 2001 Ontario Student Drug Use Survey (n=1322). Physical activity is measured by the number of days of vigorous physical activity during the past 7 days.
  
  
  RESULTS
  In both samples, there was a dominant and steady decline in physical activity between ages 14 and 18 years. The number of activity days was higher in the U.S. than in Ontario holding constant age and sex. However, a significant sample-by-age interaction showed that the decline in the percentage of U.S. students reporting 3 or more physical activity days was greater than it was in Ontario.
  
  
  CONCLUSIONS
  While the pattern of decline was shown to be similar, the decline was stronger among US adolescents. Future research should examine additional factors influencing the decline in activity and the optimal timing of programs to reduce the decline.
authors: Physical Activity Research Program, Department of Public Health Sciences, Faculty of Medicine, University of Toronto, Toronto, ON. k.allison@utoronto.ca
authors: Kenneth R
authors: KR
authors: Allison
authors: Edward M
authors: EM
authors: Adlaf
authors: John J M
authors: JJ
authors: Dwyer
authors: Daria C
authors: DC
authors: Lysy
authors: Hyacinth M
authors: HM
authors: Irving
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000208:ethnology*; D000367:Age Factors; D040343:Behavioral Risk Factor Surveillance System; D002170:Canada; D005260:Female; D015438:Health Behavior / Q000208:ethnology*; D006801:Humans; D008297:Male; D009043:Motor Activity; D011634:Public Health; D012737:Sex Factors; D013334:Students / Q000706:statistics & numerical data*; D014481:United States