title: Screen time viewing behaviors and isometric trunk muscle strength in youth.
abstract: OBJECTIVE
  The objective of this study was to examine the association of screen time viewing behavior with isometric trunk muscle strength in youth.
  
  
  METHODS
  A cross-sectional study was carried out including 606 adolescents (14-16 yr old) participating in the Danish European Youth Heart Study, a population-based study with assessments conducted in either 1997/1998 or 2003/2004. Maximal voluntary contractions during isometric back extension and abdominal flexion were determined using a strain gauge dynamometer, and cardiorespiratory fitness (CRF) was obtained using a maximal cycle ergometer test. TV viewing time, computer use, and other lifestyle behaviors were obtained by self-report. Analyses of association of screen use behaviors with isometric trunk muscle strength were carried out using multivariable adjusted linear regression.
  
  
  RESULTS
  The mean (SD) isometric strength was 0.87 (0.16) N·kg-1. TV viewing, computer use, and total screen time use were inversely associated with isometric trunk muscle strength in analyses adjusted for lifestyle and sociodemographic factors. After further adjustment for CRF and waist circumference, associations remained significant for computer use and total screen time, but TV viewing was only marginally associated with muscle strength after these additional adjustments (-0.05 SD (95% confidence interval, -0.11 to 0.005) difference in strength per 1 h·d-1 difference in TV viewing time, P = 0.08). Each 1 h·d-1 difference in total screen time use was associated with -0.09 SD (95% confidence interval, -0.14 to -0.04) lower isometric trunk muscle strength in the fully adjusted model (P = 0.001). There were no indications that the association of screen time use with isometric trunk muscle strength was attenuated among highly fit individuals (P = 0.91 for CRF by screen time interaction).
  
  
  CONCLUSIONS
  Screen time use was inversely associated with isometric trunk muscle strength independent of CRF and other confounding factors.
authors.affiliation: 1Research Unit for Exercise Epidemiology, Department of Sport Science and Clinical Biomechanics, Center of Research in Childhood Health, University of Southern Denmark, Odense, DENMARK; 2Medical Research Council Epidemiology Unit, Institute of Metabolic Science, Cambridge, England, UNITED KINGDOM; and 3Department of Sports Medicine, Norwegian School of Sport Sciences, Oslo, NORWAY.
authors.forename: Anders
authors.initials: A
authors.lastname: Grøntved
authors.forename: Mathias
authors.initials: M
authors.lastname: Ried-Larsen
authors.forename: Karsten
authors.initials: K
authors.lastname: Froberg
authors.forename: Niels
authors.initials: N
authors.lastname: Wedderkopp
authors.forename: Søren
authors.initials: S
authors.lastname: Brage
authors.forename: Peter Lund
authors.initials: PL
authors.lastname: Kristensen
authors.forename: Lars Bo
authors.initials: LB
authors.lastname: Andersen
authors.forename: Niels Christian
authors.initials: NC
authors.lastname: Møller
mesh_terms: D000293:Adolescent; D003201:Computers / Q000706:statistics & numerical data; D003430:Cross-Sectional Studies; D003718:Denmark; D005080:Exercise Test; D005260:Female; D015438:Health Behavior; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000502:physiology*; D010809:Physical Fitness; D011795:Surveys and Questionnaires; D013690:Television / Q000706:statistics & numerical data; D013997:Time Factors; D060726:Torso / Q000502:physiology*