title: Genetic and environmental causes of tracking in explosive strength during adolescence.
abstract: OBJECTIVE
  To determine whether the observed phenotypic stability in explosive strength during adolescence, as measured by inter-age correlations in vertical jump (VTJ), is mainly caused by genetic and/or environmental factors.
  
  
  METHODS
  Subjects are from the Leuven Longitudinal Twin Study (LLTS) (n = 105 pairs, equally divided over five zygosity groups). VTJ data were aligned on age at peak height velocity (APHV) to attenuate the temporal fluctuations in inter-age correlations caused by differences in timing of the adolescent growth spurt. Simplex models were fitted using structural equation modelling.
  
  
  RESULTS
  After aligning the data on APHV, the annual inter-age correlations show a clear simplex structure over a 4 year interval. The best fitting models included additive genetic and unique environmental sources of variation. Heritability estimates ranged between 60.8% (CI 37.7%-77.2%) and 87.3% (CI 74.2%-94.0%) for boys and between 76.5% (CI 56.7%-89.0%) and 88.6% (CI 77.8%-94.1%) for girls. Up to 56.4% and 62.8% of the total variation at the last measurement occasion is explained by additive genetic factors that already explained a significant amount of variation at previous measurement occasions in boys and girls respectively. It thus can be concluded that the observed stability of explosive strength during adolescence is mainly caused by a stable genetic influence in boys and girls.
  
  
  CONCLUSIONS
  Additive genetic factors seem to be the main cause of the observed phenotypic stability in VTJ performance in boys and girls during adolescence.
authors.affiliation: Faculty of Kinesiology and Rehabilitation Sciences, Katholieke Universiteit Leuven, Tervuursevest 101, B-3001, Leuven, Belgium. Maarten.Peeters@faber.kuleuven.be
authors.forename: Maarten W
authors.initials: MW
authors.lastname: Peeters
authors.forename: Martine A
authors.initials: MA
authors.lastname: Thomis
authors.forename: Hermine H M
authors.initials: HH
authors.lastname: Maes
authors.forename: Ruth J F
authors.initials: RJ
authors.lastname: Loos
authors.forename: Albrecht L
authors.initials: AL
authors.lastname: Claessens
authors.forename: Robert
authors.initials: R
authors.lastname: Vlietinck
authors.forename: Gaston P
authors.initials: GP
authors.lastname: Beunen
mesh_terms: D000293:Adolescent; D041923:Adolescent Development; D002648:Child; D004777:Environment; D005260:Female; D005500:Follow-Up Studies; D014644:Genetic Variation; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008954:Models, Biological; D008957:Models, Genetic; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010641:Phenotype; D010809:Physical Fitness / Q000502:physiology*; D019655:Quantitative Trait, Heritable; D012737:Sex Factors; D014427:Twins / Q000235:genetics / Q000502:physiology*