title: Multilevel analyses of school and children's characteristics associated with physical activity.
abstract: BACKGROUND
  Children spend most of their awake time at school, and it is important to identify individual and school-level correlates of their physical activity (PA) levels. This study aimed to identify the between-school variability in Portuguese children PA and to investigate student and school PA correlates using multilevel modeling.
  
  
  METHODS
  The sample included 1075 Portuguese children of both sexes, aged 6-10 years, from 24 schools. Height and weight were measured and body mass index (BMI) was estimated. Physical activity was estimated using the Godin and Shephard questionnaire (total PA score was used); cardiorespiratory fitness was estimated with the 1-mile run/walk test. A structured inventory was used to access information about the school environment. A multilevel analysis (level-1: student-level; level-2: school-level) was used.
  
  
  RESULTS
  Student-level variables (age, sex, 1-mile run/walk test) explained 7% of the 64% variance fraction of the individual-level PA; however, school context explained approximately 36% of the total PA variance. Variables included in the model (school size, school setting, playground area, frequency and duration of physical education class, and qualification of physical education teacher) are responsible for 80% of the context variance.
  
  
  CONCLUSIONS
  School environment is an important correlate of PA among children, enhancing children's opportunities for being active and healthy.
authors.affiliation: Faculty of Sport, University of Porto, Rua Dr. Plácido Costa, 91, 4200-450 Porto, Portugal. thayse_natacha@hotmail.com.
authors.forename: Thayse Natacha
authors.initials: TN
authors.lastname: Gomes
authors.forename: Fernanda K
authors.initials: FK
authors.lastname: dos Santos
authors.forename: Weimo
authors.initials: W
authors.lastname: Zhu
authors.forename: Joey
authors.initials: J
authors.lastname: Eisenmann
authors.forename: José A R
authors.initials: JA
authors.lastname: Maia
mesh_terms: D000367:Age Factors; D015992:Body Mass Index; D001837:Body Weights and Measures; D002648:Child; D004777:Environment; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D055361:Multilevel Analysis; D010806:Physical Education and Training; D010988:Play and Playthings; D011174:Portugal; D012111:Residence Characteristics; D012574:Schools / Q000706:statistics & numerical data*; D012737:Sex Factors; D012959:Socioeconomic Factors
keywords: correlates; exercise; hierarchical linear modeling; youth