title: Temporal relationships between screen-time and physical activity with cardiorespiratory fitness in English schoolchildren: a 2-year longitudinal study.
abstract: OBJECTIVE
  To determine the temporal relationships screen-time and physical activity have with cardiorespiratory fitness.
  
  
  METHODS
  Measures were made over two years (2008-2010) in 1500 participants aged 11.5 (SD 0.5) years at baseline.
  
  
  RESULTS
  Tracking coefficients were low-to-moderate for all measures. At follow-up, 25% of participants moved from having low (<2h) to high (≥ 2 h) daily screen-time and 6% became unfit according to FITNESSGRAM standards. Baseline screen-time was the strongest univariate predictor of becoming unfit. Multivariate analysis controlling for decimal age, BMI and deprivation confirmed baseline screen-time as the strongest independent predictor of becoming unfit over the 2-year study period (OR 2.4; 95%CI:1.4-4.0). Current (OR 2.3; 95%CI:1.3-4.0) and previous (OR 1.7; 95%CI:1.0-2.9) physical activity levels also independently predicted becoming unfit.
  
  
  CONCLUSIONS
  There is currently no guidance for limiting screen-time in UK children. These longitudinal data add to the cross-sectional evidence of lower physical activity and fitness in children reporting ≥ 2 h daily screen-time. More importantly, these data demonstrate that high screen-time during childhood is an independent predictor of lower cardiorespiratory fitness in adolescence.
authors.affiliation: Department of Biological Sciences, University of Essex, UK.
authors.forename: D
authors.initials: D
authors.lastname: Aggio
authors.forename: A A
authors.initials: AA
authors.lastname: Ogunleye
authors.forename: C
authors.initials: C
authors.lastname: Voss
authors.forename: G R H
authors.initials: GR
authors.lastname: Sandercock
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D015992:Body Mass Index; D002302:Cardiac Output / Q000502:physiology*; D002318:Cardiovascular Diseases / Q000517:prevention & control; D002648:Child; D004739:England; D015444:Exercise / Q000502:physiology / Q000523:psychology*; D005080:Exercise Test; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D015999:Multivariate Analysis; D010101:Oxygen Consumption / Q000502:physiology; D012572:School Health Services; D057185:Sedentary Behavior; D017678:Sex Distribution; D013334:Students / Q000523:psychology* / Q000706:statistics & numerical data; D011795:Surveys and Questionnaires; D013690:Television / Q000706:statistics & numerical data*; D013997:Time Factors