title: Sagittal plane body kinematics and kinetics during single-leg landing from increasing vertical heights and horizontal distances: implications for risk of non-contact ACL injury.
abstract: OBJECTIVE
  This study identified kinematic and knee energetic variables that reduce the risk of non-contact anterior cruciate ligament (ACL) injury during single-leg landings from increasing vertical heights and horizontal distances.
  
  
  METHODS
  Nine subjects performed single-leg landings from takeoff platforms with vertical heights of 20, 40, and 60 cm onto a force plate. Subjects also performed single-leg landings from a 40 cm high takeoff platform placed at horizontal distances of 30, 50 and 70 cm from a force plate. Kinematic and kinetic data were measured.
  
  
  RESULTS
  Vertical height had a significant and positive effect on peak vertical ground reaction force (VGRF) (p<0.001), peak posterior ground reaction force (PGRF) (p=0.004), knee flexion angle (p=0.0043), trunk flexion angle (p=0.03), knee power (p<0.001) and knee work (p<0.001). There was also a significant and positive effect of horizontal distance on peak PGRF (p<0.001), ankle plantar flexion angle (p=0.008), hip flexion angle (p=0.007), and trunk flexion angle (p=0.001). At increasing vertical height, peak VGRF was significantly correlated to ankle plantar flexion and knee flexion angles (r=-0.77, p=0.02 and r=-0.78, p=0.01, respectively). At increasing horizontal distance, peak PGRF was significantly correlated to ankle plantar flexion angle, knee power and knee work (r=-0.85, p=0.003; r=0.67, p=0.04; and r=0.73, p=0.02, respectively).
  
  
  CONCLUSIONS
  A better understanding of the risk factors to non-contact ACL injury during single-leg landings from increasing vertical heights and horizontal distances can aid in the design of injury prevention regimen.
authors.affiliation: School of Human Kinetics, University of Ottawa, Ottawa, Canada. Electronic address: nali065@uottawa.ca.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Ali
authors.affiliation: School of Human Kinetics, University of Ottawa, Ottawa, Canada.
authors.forename: D Gordon E
authors.initials: DG
authors.lastname: Robertson
authors.affiliation: School of Human Kinetics, University of Ottawa, Ottawa, Canada; Faculty of Biomedical Engineering, Amirkabir University of Technology, Tehran, Iran.
authors.forename: Gholamreza
authors.initials: G
authors.lastname: Rouhi
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D016118:Anterior Cruciate Ligament / Q000503:physiopathology; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena / Q000502:physiology; D006801:Humans; D007596:Joints / Q000502:physiology*; D007700:Kinetics; D007718:Knee Injuries / Q000503:physiopathology / Q000517:prevention & control*; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D018570:Risk Assessment; D012307:Risk Factors; D060726:Torso / Q000502:physiology