title: [Determinants of adolescents' physical activity].
abstract: OBJECTIVE
  To compare the study results concerning the correct level of 13- and 15-year-old adolescents physical activity and impact of selected physical activity determinants (self-efficacy, BMI, gender, domicile) obtained from two nationwide studies out in Poland, using a similar questionnaire in 2006 and 2008.
  
  
  METHODS
  The material comes from two studies. The first, the 2006 HBSC survey included 2287 15-year-old students (1092 boys and 1195 girls); the second, the 2008 third phase of a prospective, three-phase survey, included 605 13-year-olds (300 boys and 305 girls) born in Poland in January 1995. Questions on physical activity were analysed (MVPA), along with the following determinants: self-efficacy, domicile, gender, body weight and height. Cross-tabulation with chi2 analysis and multilevel modelling were applied.
  
  
  RESULTS
  Physical activity deficiency was found in both examined populations. In study I--84.8%, in study II--80.3%. Self-efficacy (p < 0.01), gender (p < 0.001) and BMI (p < 0.04) had an impact on the 15-year-olds physical activity. In 13-year-olds, only self-efficacy was close to significant relation with physical activity. The results of multilevel logistic regression in study I identified protective factors: male gender [OR = 0.41; CI (OR): 0.32-0.53] and strong self-efficacy [OR = 0.66; CI (OR): 0.51-0.85]; while being underweight was identified as a risk factor [OR = 2.77; CI (OR): 1.11-6.95]. In study II only strong self-efficacy was found as a protective factor [OR = 0.51; CI (OR): 0.30-0.89] against lack of physical activity.
  
  
  CONCLUSIONS
  Most of the examined adolescents from study I as well as study II suffered from physical activity deficiency. The share of biological determinants (gender, BMI) in maintaining correct level of physical activity increased with age. A link between physical activity and self-efficacy was demonstrated in the 15-year-olds, while this tendency was identified in the 13-year-olds. The results point to a need for implementing programmes supporting self-efficacy in children under the age of 13 and to carry out assessment of self satisfaction concerning own bodyweight. In preparing these programmes sex differences should be taken into consideration.
authors.affiliation: Zakład Ochrony i Promocji Zdrowia Dzieci i Młodziezy, Instytut Matki i Dziecka, Warszawa. hanna.kololo@imid.med.pl
authors.forename: Hanna
authors.initials: H
authors.lastname: Kołoło
authors.forename: Joanna
authors.initials: J
authors.lastname: Mazur
authors.forename: Krystyna
authors.initials: K
authors.lastname: Mikiel-Kostyra
authors.forename: Monika
authors.initials: M
authors.lastname: Guszkowska
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D005260:Female; D015438:Health Behavior; D006801:Humans; D016015:Logistic Models; D008297:Male; D009043:Motor Activity; D012307:Risk Factors; D020377:Self Efficacy