title: Physical activity trajectories and multilevel factors among adolescent girls.
abstract: OBJECTIVE
  Although the decline of physical activity in adolescent girls is well-documented, there are girls whose physical activity does not follow this pattern. This study examined the relationships between physical activity trajectories and personal, psychosocial, and environmental factors among adolescent girls.
  
  
  METHODS
  Participants were from the University of Maryland field site of the Trial of Activity for Adolescent Girls. Of 730 girls measured in 8th grade, 589 were remeasured in 11th grade. Moderate-to-vigorous physical activity was assessed by accelerometers; participants were categorized as active maintainers (n = 31), inactive maintainers (n = 410), adopters (n = 64), or relapsers (n = 56). Height and weight were measured, personal and psychosocial information was collected from surveys, and distance from home to school and parks was assessed from Geographical Information Systems. Multivariable logistic regression was used for data analysis.
  
  
  RESULTS
  Variables at individual, social, and environmental levels predicted active maintainers and inactive maintainers, while only individual-level variables predicted adoption. None predicted relapse. Higher (favorable) scores for physical self-concept, perceived body fat, friend and family physical activity support, frequency of physical activity with friends, and shorter distance from home to a park predicted active maintainers. Overweight/obese status, earlier age at menses, and lower scores for physical self-concept, perceived body fat, friend physical activity support, and frequency of physical activity with friends, and farther distance from home to school predicted inactive maintainers. High physical self-concept and not being overweight/obese predicted adopters.
  
  
  CONCLUSIONS
  Multilevel factors appear to predict behavior maintenance rather than actual change.
authors.affiliation: Goldberg Center for Pediatric Community Health, National Children's Medical Center, Washington, DC.
authors.forename: Kathleen R
authors.initials: KR
authors.lastname: Zook
authors.affiliation: Department of Epidemiology and Biostatistics, University of Maryland, College Park, Maryland.
authors.forename: Brit I
authors.initials: BI
authors.lastname: Saksvig
authors.affiliation: Department of Epidemiology and Biostatistics, University of Maryland, College Park, Maryland.
authors.forename: Tong Tong
authors.initials: TT
authors.lastname: Wu
authors.affiliation: Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, California. Electronic address: deborah.r.young@kp.org.
authors.forename: Deborah Rohm
authors.initials: DR
authors.lastname: Young
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D015444:Exercise / Q000523:psychology; D005260:Female; D006801:Humans; D016015:Logistic Models; D050177:Overweight; D000297:Psychology, Adolescent; D012649:Self Concept
keywords: Adolescence; Longitudinal study; Physical activity