title: Strength imbalances and prevention of hamstring injury in professional soccer players: a prospective study.
abstract: BACKGROUND
  The relationship between muscle injury and strength disorders remains a matter of controversy.
  
  
  OBJECTIVE
  Professional soccer players performed a preseason isokinetic testing aimed at determining whether (1) strength variables could be predictors of subsequent hamstring strain and (2) normalization of strength imbalances could reduce the incidence of hamstring injury.
  
  
  METHODS
  Cohort study (prognosis); Level of evidence, 1.
  
  
  METHODS
  A standardized concentric and eccentric isokinetic assessment was used to identify soccer players with strength imbalances. Subjects were classified among 4 subsets according to the imbalance management content. Recording subsequent hamstring injuries allowed us to define injury frequencies and relative risks between groups.
  
  
  RESULTS
  Of 687 players isokinetically tested in preseason, a complete follow-up was obtained in 462 players, for whom 35 hamstring injuries were recorded. The rate of muscle injury was significantly increased in subjects with untreated strength imbalances in comparison with players showing no imbalance in preseason (relative risk = 4.66; 95% confidence interval: 2.01-10.8). The risk of injury remained significantly higher in players with strength imbalances who had subsequent compensating training but no final isokinetic control test than in players without imbalances (relative risk = 2.89; 95% confidence interval: 1.00-8.32). Conversely, normalizing the isokinetic parameters reduced the risk factor for injury to that observed in players without imbalances (relative risk = 1.43; 95% confidence interval: 0.44-4.71).
  
  
  CONCLUSIONS
  The outcomes showed that isokinetic intervention gives rise to the preseason detection of strength imbalances, a factor that increases the risk of hamstring injury. Restoring a normal strength profile decreases the muscle injury incidence.
authors.affiliation: Department of Motricity Sciences and Rehabilitation, University and CHU of Liege, Liege, Belgium. jlcroisier@ulg.ac.be
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Croisier
authors.forename: Sebastien
authors.initials: S
authors.lastname: Ganteaume
authors.forename: Johnny
authors.initials: J
authors.lastname: Binet
authors.forename: Marc
authors.initials: M
authors.lastname: Genty
authors.forename: Jean-Marcel
authors.initials: JM
authors.lastname: Ferret
mesh_terms: D000328:Adult; D001265:Athletic Injuries / Q000503:physiopathology / Q000517:prevention & control*; D007839:Functional Laterality; D006801:Humans; D007866:Leg; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000293:injuries* / Q000503:physiopathology; D011446:Prospective Studies; D012916:Soccer / Q000293:injuries*