title: Predicting factors of physical activity in adolescents: a systematic review.
abstract: OBJECTIVE
  The main goal of this systematic review is to summarize and identify the current literature that addresses factors associated with adolescents' physical activity.
  
  
  METHODS
  A systematic review of the literature was undertaken using a reference period between 1998 and 2008, based primarily on the PubMed/CINAHL/PsycINFO/ProQuest databases. A total of 35 articles were considered appropriate for this review.
  
  
  RESULTS
  This systematic review found some evidence of associations between physical activity and the following variables: age, sex, parental education level, socioeconomic status, self-efficacy, perceived benefits, perceived barriers, perceived behavior control, parental support, parent modeling, peer support, past physical activity, depressive symptoms, smoking, alcohol consumption, and environmental determinants.
  
  
  CONCLUSIONS
  Some variables have been studied too few times to deduce any conclusion, so more research is needed to test variables. Variables that did not have consistent results also need further testing.
authors.affiliation: Professor, College of Nursing, Pusan National University, Busan, Korea.
authors.forename: Hyoungsook
authors.initials: H
authors.lastname: Park
authors.affiliation: Pre-Doctorate Fellow, School of Nursing, University of Michigan, Michigan, USA.
authors.forename: Namhee
authors.initials: N
authors.lastname: Kim