title: Lower extremity mechanics during landing after a volleyball block as a risk factor for anterior cruciate ligament injury.
abstract: OBJECTIVE
  To compare lower extremity mechanics and energy absorption during two types of landing after a successful or unsuccessful block in volleyball and assess the risks of anterior cruciate ligament (ACL) injury.
  
  
  METHODS
  Cohort study.
  
  
  METHODS
  Fourteen elite male volleyball players (aged 24.5 ± 4.6 years; height 1.94 ± 0.06 m; mass 86.6 ± 7.6 kg).
  
  
  METHODS
  Subjects were required to land on force platforms using stick landing or step-back landing (with the right lower extremity stepping back away from the net) techniques after performing a standing block jump movement.
  
  
  METHODS
  Vertical ground reaction force (body weight); knee flexion (degrees); knee moments (Nm/kg); and hip, knee and ankle energy absorption (J/kg).
  
  
  RESULTS
  The right lower extremity showed a greater first peak of vertical ground reaction force, a greater valgus moment, lower energy absorption by the knee, and higher energy absorption by the hip and ankle joints during step-back landing.
  
  
  CONCLUSIONS
  The lower extremity may be exposed to a greater risk of ACL injury when stepping back from the net during the initial impact phase after a step-back landing.
authors.affiliation: Human Motion Diagnostic Center, University of Ostrava, Varenska 40A, 70200 Ostrava, Czech Republic. Electronic address: david.zahradnik@osu.cz.
authors.forename: David
authors.initials: D
authors.lastname: Zahradnik
authors.affiliation: Human Motion Diagnostic Center, University of Ostrava, Varenska 40A, 70200 Ostrava, Czech Republic.
authors.forename: Daniel
authors.initials: D
authors.lastname: Jandacka
authors.affiliation: Human Motion Diagnostic Center, University of Ostrava, Varenska 40A, 70200 Ostrava, Czech Republic.
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Uchytil
authors.affiliation: Human Motion Diagnostic Center, University of Ostrava, Varenska 40A, 70200 Ostrava, Czech Republic.
authors.forename: Roman
authors.initials: R
authors.lastname: Farana
authors.affiliation: Biomechanics Laboratory, University of Massachusetts, Amherst, MA, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Hamill
mesh_terms: D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D015331:Cohort Studies; D006801:Humans; D035002:Lower Extremity; D008297:Male; D011187:Posture; D012307:Risk Factors; D054798:Volleyball; D014947:Wounds and Injuries / Q000209:etiology*; D055815:Young Adult
keywords: Injury prevention; Knee; Landing; Lower extremity