Trajectories of physical activity in Montreal adolescents from age 12 to 17 years.
BACKGROUND
Despite the benefits of physical activity, many Canadian adolescents are inactive and rates of inactivity increase with age. Few studies describe the pattern of change in physical activity as a function of age during adolescence.


METHODS
Data were drawn from the Nicotine Dependence in Teens Study. The analytic sample included 1206 adolescents who completed a 7-day physical activity recall up to 4 times per year over 5 years. Individual growth models, analyzed using multilevel models for change, were developed separately by sex controlling for season.


RESULTS
Physical activity levels through adolescence were best described by a cubic function. Levels increased from age 12 to a peak at approximately age 13.5, decreased to age 16.5, and increased again to age 17. Activity participation was highest in the spring and lowest during fall and winter. Substantial within- and between-subject heterogeneity in the trajectories was evident.


CONCLUSIONS
Adolescent physical activity follows a complex, curvilinear pattern in both males and females, with considerable variation within- and between-persons.
Health Analysis Division, Statistics Canada, Ottawa, Ontario, Canada.
Kellie A
KA
Langlois
Nicholas
N
Birkett
Rochelle
R
Garner
Jennifer
J
O'Loughlin
D000293:Adolescent; D000294:Adolescent Behavior; D002648:Child; D005260:Female; D015438:Health Behavior; D006801:Humans; D008297:Male; D011939:Mental Recall; D008962:Models, Theoretical; D009043:Motor Activity / Q000502:physiology*; D011446:Prospective Studies; D011792:Quebec; D012621:Seasons; D013223:Statistics as Topic; D011795:Surveys and Questionnaires; D014505:Urban Population