title: Fatigue-induced balance impairment in young soccer players.
abstract: BACKGROUND
  Although balance is generally recognized to be an important feature in ensuring good performance in soccer, its link with functional performance remains mostly unexplored, especially in young athletes.
  
  
  OBJECTIVE
  To investigate changes in balance induced by fatigue for unipedal and bipedal static stances in young soccer players.
  
  
  METHODS
  Crossover study.
  
  
  METHODS
  Biomechanics laboratory and outdoor soccer field.
  
  
  METHODS
  Twenty-one male soccer players (age = 14.5 ± 0.2 years, height = 164.5 ± 5.6 cm, mass = 56.8 ± 6.8 kg).
  
  
  METHODS
  Static balance was assessed with postural-sway analysis in unipedal and bipedal upright stance before and after a fatigue protocol consisting of a repeated sprint ability (RSA) test (2 × 15-m shuttle sprint interspersed with 20 seconds of passive recovery, repeated 6 times).
  
  
  METHODS
  On the basis of the center-of-pressure (COP) time series acquired during the experimental tests, we measured sway area, COP path length, and COP maximum displacement and velocity in the anteroposterior and mediolateral directions.
  
  
  RESULTS
  Fatigue increased all sway values in bipedal stance and all values except COP velocity in the mediolateral direction in unipedal stance. Fatigue index (calculated on the basis of RSA performance) was positively correlated with fatigue/rest sway ratio for COP path length and COP velocity in the anteroposterior and mediolateral directions for nondominant single-legged stance.
  
  
  CONCLUSIONS
  Fatigued players exhibited reduced performance of the postural-control system. Participants with better performance in the RSA test appeared less affected by balance impairment, especially in single-legged stance.
authors.affiliation: University of Cagliari, Italy.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Pau
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Ibba
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Attene
mesh_terms: D000293:Adolescent; D056352:Athletes; D054874:Athletic Performance / Q000502:physiology*; D018592:Cross-Over Studies; D005221:Fatigue / Q000503:physiopathology*; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D004856:Postural Balance / Q000502:physiology*; D012916:Soccer / Q000502:physiology*; D055815:Young Adult
keywords: athletes; postural sway; repeated sprint ability test