title: Strength asymmetry of the shoulders in elite volleyball players.
abstract: BACKGROUND
  Volleyball players are reported to have shoulder strength imbalances. Previous authors have primarily investigated small samples of male players at a single skill level, without considering playing position, and with inconsistent findings.
  
  
  OBJECTIVE
  To evaluate shoulder strength asymmetry and a history of shoulder injury in a large sample of professional volleyball players of both sexes across different playing positions and skill levels.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  A sample of 183 volleyball players (99 men, 84 women).
  
  
  METHODS
  We assessed shoulder internal-rotator and external-rotator concentric strength at 60°/s using an isokinetic dynamometer and dominant-nondominant differences in shoulder strength and strength ratios using repeated-measures analyses of variance. Peak torque was normalized for body mass and external-rotation/internal-rotation concentric strength.
  
  
  RESULTS
  Internal-rotation strength was asymmetric in favor of the dominant side in both sexes, regardless of previous shoulder injury status. Male volleyball players had a lower shoulder strength ratio on the dominant side, regardless of previous shoulder injury status. However, this finding was valid only when hand dominance was taken into account. Female volleyball players playing at a higher level (ie, first versus second division) were 3.43 times more likely to have an abnormal strength ratio. Playing position was not associated with an abnormal shoulder strength ratio or strength asymmetry.
  
  
  CONCLUSIONS
  In male volleyball players, the external-rotation/internal-rotation strength ratio of the dominant shoulder was lower, regardless of playing position, skill level, or a previous shoulder injury. In female players, the ratio was less only in those at a higher skill level. Although speculative, these findings generally suggest that female volleyball players could have a lower risk of developing shoulder-related problems than male volleyball players. Isokinetic shoulder testing may reveal important information about the possible risk factors for shoulder injuries, so we recommend including it in the functional screening of volleyball players.
authors.affiliation: Faculty of Sport, University of Ljubljana, Slovenia.
authors.forename: Vedran
authors.initials: V
authors.lastname: Hadzic
authors.forename: Tine
authors.initials: T
authors.lastname: Sattler
authors.forename: Matjaž
authors.initials: M
authors.lastname: Veselko
authors.forename: Goran
authors.initials: G
authors.lastname: Markovic
authors.forename: Edvin
authors.initials: E
authors.lastname: Dervisevic
mesh_terms: D000293:Adolescent; D000328:Adult; D004292:Dominance, Cerebral / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000502:physiology*; D011187:Posture / Q000502:physiology; D012399:Rotation; D012727:Sex Characteristics; D012782:Shoulder / Q000502:physiology*; D019415:Torque; D054798:Volleyball / Q000502:physiology*; D055815:Young Adult
keywords: injury prevention; isokinetic testing; muscle imbalances; muscle strength