title: Longitudinal predictors of aerobic performance in adolescent soccer players.
abstract: BACKGROUND
  The importance of aerobic performance in youth soccer is well established. The aim of the present study was to evaluate the contributions of chronological age (CA), skeletal age (SA), body size, and training to the longitudinal development of aerobic performance in youth male soccer players aged 10 to 18 years.
  
  
  METHODS
  Players (n=83) were annually followed up during 5 years, resulting in an average of 4.4 observations per player. Decimal CA was calculated, and SA, stature, body weight, and aerobic performance were measured once per year. Fat-free mass (FFM) was estimated from age- and gender-specific anthropometric formulas, and annual volume training was recorded. After testing for multicollinearity, multilevel regression modeling was used to analyze the longitudinal data aligned by CA and SA (Model 1 and 2, respectively) and to develop aerobic performance scores.
  
  
  RESULTS
  The following equations provide estimations of the aerobic performance for young soccer players: ŷ(Model 1 [deviance from the null model =388.50; P<0.01]) =57.75+9.06×centered CA-0.57×centered CA(2)+0.03×annual volume training and ŷ(Model 2 [deviance from the null model=327.98; P<0.01])=13.03+4.04×centered SA-0.12×centered SA(2)+0.99×FFM+0.03×annual volume training.
  
  
  CONCLUSIONS
  The development of aerobic performance in young soccer players was found to be significantly related to CA, biological development, and volume of training.
authors.affiliation: Faculty of Sport Sciences and Physical Education, University of Coimbra, Portugal.
authors.forename: João
authors.initials: J
authors.lastname: Valente-dos-Santos
authors.forename: Manuel J
authors.initials: MJ
authors.lastname: Coelho-e-Silva
authors.forename: João
authors.initials: J
authors.lastname: Duarte
authors.forename: António J
authors.initials: AJ
authors.lastname: Figueiredo
authors.forename: João R
authors.initials: JR
authors.lastname: Liparotti
authors.forename: Lauren B
authors.initials: LB
authors.lastname: Sherar
authors.forename: Marije T
authors.initials: MT
authors.lastname: Elferink-Gemser
authors.forename: Robert M
authors.initials: RM
authors.lastname: Malina
mesh_terms: D000293:Adolescent; D000367:Age Factors; D054874:Athletic Performance / Q000502:physiology*; D050218:Body Fat Distribution; D001835:Body Weight; D002648:Child; D015444:Exercise; D006801:Humans; D008297:Male; D011379:Prognosis; D012916:Soccer / Q000502:physiology*