title: The effects of 2 landing techniques on knee kinematics, kinetics, and performance during stop-jump and side-cutting tasks.
abstract: BACKGROUND
  Anterior cruciate ligament injuries (ACL) commonly occur during jump landing and cutting tasks. Attempts to land softly and land with greater knee flexion are associated with decreased ACL loading. However, their effects on performance are unclear.
  
  
  OBJECTIVE
  Attempts to land softly will decrease peak posterior ground-reaction force (PPGRF) and knee extension moment at PPGRF compared with a natural landing during stop-jump and side-cutting tasks. Attempts to land with greater knee flexion at initial ground contact will increase knee flexion at PPGRF compared with a natural landing during both tasks. In addition, both landing techniques will increase stance time and lower extremity mechanical work as well as decrease jump height and movement speed compared with a natural landing during both tasks.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  A total of 18 male and 18 female recreational athletes participated in the study. Three-dimensional kinematic and kinetic data were collected during stop-jump and side-cutting tasks under 3 conditions: natural landing, soft landing, and landing with greater knee flexion at initial ground contact.
  
  
  RESULTS
  Attempts to land softly decreased PPGRF and knee extension moment at PPGRF compared with a natural landing during stop-jump tasks. Attempts to land softly decreased PPGRF compared with a natural landing during side-cutting tasks. Attempts to land with greater knee flexion at initial ground contact increased knee flexion angle at PPGRF compared with a natural landing during both stop-jump and side-cutting tasks. Attempts to land softly and land with greater knee flexion at initial ground contact increased stance time and lower extremity mechanical work, as well as decreased jump height and movement speed during both stop-jump and side-cutting tasks.
  
  
  CONCLUSIONS
  Although landing softly and landing with greater knee flexion at initial ground contact may reduce ACL loading during stop-jump and side-cutting tasks, the performance of these tasks decreased, as indicated by increased stance time and mechanical work as well as decreased jump height and movement speed.
  
  
  CONCLUSIONS
  Training effects tested in laboratory environments with the focus on reducing ACL loading may be reduced in actual competition environments when the focus is on athlete performance. The effects of training programs for ACL injury prevention on lower extremity biomechanics in athletic tasks may need to be evaluated in laboratories as well as in actual competitions.
authors.affiliation: Division of Kinesiology and Health, University of Wyoming, Laramie, Wyoming, USA.
authors.forename: Boyi
authors.initials: B
authors.lastname: Dai
authors.affiliation: Department of Orthopaedic Surgery, Duke University, Durham, North Carolina, USA.
authors.forename: William E
authors.initials: WE
authors.lastname: Garrett
authors.affiliation: Division of Physical Therapy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Gross
authors.affiliation: Department of Exercise and Sport Science, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
authors.forename: Darin A
authors.initials: DA
authors.lastname: Padua
authors.affiliation: Department of Orthopaedic Surgery, Duke University, Durham, North Carolina, USA.
authors.forename: Robin M
authors.initials: RM
authors.lastname: Queen
authors.affiliation: Division of Physical Therapy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA bing_yu@med.unc.edu.
authors.forename: Bing
authors.initials: B
authors.lastname: Yu
mesh_terms: D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries; D054874:Athletic Performance / Q000502:physiology*; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007700:Kinetics; D007718:Knee Injuries / Q000517:prevention & control; D007719:Knee Joint / Q000502:physiology*; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*; D055815:Young Adult
keywords: ACL injuries; biomechanics; cutting; jump landing; performance