title: A Longitudinal Study of Physical Fitness in Elite Junior Tennis Players.
abstract: To analyze how physical fitness (PF) improves in elite junior tennis players related to age, maturity, and performance level.
  
  
  
  Elite junior tennis players (n = 113 boys, n = 83 girls) divided by performance level were monitored longitudinally from U14 to U16. Maturity, upper and lower-body power, speed, and agility were measured during subsequent competitive seasons. Improvement was analyzed per sex using multilevel analysis.
  
  
  
  PF components for boys and girls improved over age (U14-U16) (ES .53-.97). In boys, the more mature boys outscored the less mature boys in upper and lower-body power from U14-U16. In girls, high-ranked girls outscored lower-ranked girls on lower-body power, speed, and agility (U14-U16) (p < .05).
  
  
  
  Boys and girls improved on all PF components during U14-U16. In boys, power was related to maturity. In girls, lower-body power, speed, and agility were related to tennis performance. This has important implications for talent development.
authors.affiliation: 1 HAN University of Applied Sciences.
authors.forename: Tamara
authors.initials: T
authors.lastname: Kramer
authors.affiliation: 2 University Medical Center Groningen.
authors.forename: Barbara C H
authors.initials: BC
authors.lastname: Huijgen
authors.affiliation: 2 University Medical Center Groningen.
authors.forename: Marije T
authors.initials: MT
authors.lastname: Elferink-Gemser
authors.affiliation: 2 University Medical Center Groningen.
authors.forename: Chris
authors.initials: C
authors.lastname: Visscher
mesh_terms: D000293:Adolescent; D056352:Athletes; D054874:Athletic Performance; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D010809:Physical Fitness; D013715:Tennis
keywords: adolescence; sport; talent identification; youth