title: Fitness determinants of repeated-sprint ability in highly trained youth football players.
abstract: Variations in rates of growth and development in young football players can influence relationships among various fitness qualities.
  
  
  OBJECTIVE
  To investigate the relationships between repeated-sprint ability and other fundamental fitness qualities of acceleration, agility, explosive leg power, and aerobic conditioning through the age groups of U11 to U18 in highly trained junior football players.
  
  
  METHODS
  Male players (n = 119) across the age groups completed a fitness assessment battery over two testing sessions. The first session consisted of countermovement jumps without and with arm swing, 15-m sprint run, 15-m agility run, and the 20-m Shuttle Run (U11 to U15) or the Yo-Yo Intermittent Recovery Test, Level 1 (U16 to U18). The players were tested for repeated-sprint ability in the second testing session using a protocol of 6 × 30-m sprints on 30 s with an active recovery.
  
  
  RESULTS
  The correlations of repeated-sprint ability with the assorted fitness tests varied considerably between the age groups, especially for agility (r = .02 to .92) and explosive leg power (r = .04 to .84). Correlations of repeated sprint ability with acceleration (r = .48 to .93) and aerobic conditioning (r = .28 to .68) were less variable with age.
  
  
  CONCLUSIONS
  Repeated-sprint ability associates differently with other fundamental fitness tests throughout the teenage years in highly trained football players, although stabilization of these relationships occurs by the age of 18 y. Coaches in junior football should prescribe physical training accounting for variations in short-term disruptions or impairment of physical performance during this developmental period.
authors.affiliation: Norwegian Research Centre for Training and Performance, Norwegian School of Sports Sciences, Oslo, Norway.
authors.forename: Matt
authors.initials: M
authors.lastname: Spencer
authors.forename: David
authors.initials: D
authors.lastname: Pyne
authors.forename: Juanma
authors.initials: J
authors.lastname: Santisteban
authors.forename: Iñigo
authors.initials: I
authors.lastname: Mujika
mesh_terms: D000054:Acceleration; D000293:Adolescent; D054874:Athletic Performance / Q000502:physiology*; D002648:Child; D005080:Exercise Test; D005538:Football / Q000502:physiology*; D006801:Humans; D008297:Male; D010806:Physical Education and Training; D010809:Physical Fitness / Q000502:physiology*; D012420:Running / Q000502:physiology*