title: Changing Sagittal-Plane Landing Styles to Modulate Impact and Tibiofemoral Force Magnitude and Directions Relative to the Tibia.
abstract: BACKGROUND
  Ground reaction force (GRF) and tibiofemoral force magnitudes and directions have been shown to affect anterior cruciate ligament loading during landing. However, the kinematic and kinetic factors modifying these 2 forces during landing are unknown.
  
  
  OBJECTIVE
  To clarify the intersegmental kinematic and kinetic links underlying the alteration of the GRF and tibiofemoral force vectors secondary to changes in the sagittal-plane body position during single-legged landing.
  
  
  METHODS
  Crossover study.
  
  
  METHODS
  Laboratory.
  
  
  METHODS
  Twenty recreationally active participants (age = 23.4 ± 3.6 years, height = 171.0 ± 9.4 cm, mass = 73.3 ± 12.7 kg).
  
  
  METHODS
  Participants performed single-legged landings using 3 landing styles: self-selected landing (SSL), body leaning forward and landing on the toes (LFL), and body upright with flat-footed landing (URL). Three-dimensional kinetics and kinematics were recorded.
  
  
  METHODS
  Sagittal-plane tibial inclination and knee-flexion angles, GRF magnitude and inclination angles relative to the tibia, and proximal tibial forces at peak tibial axial forces.
  
  
  RESULTS
  The URL resulted in less time to peak tibial axial forces, smaller knee-flexion angles, and greater magnitude and a more anteriorly inclined GRF vector relative to the tibia than did the SSL. These changes led to the greatest peak tibial axial and anterior shear forces in the URL among the 3 landing styles. Conversely, the LFL resulted in longer time to peak tibial axial forces, greater knee-flexion angles, and reduced magnitude and a more posteriorly inclined GRF vector relative to the tibia than the SSL. These changes in LFL resulted in the lowest peak tibial axial and largest posterior shear forces among the 3 landing styles.
  
  
  CONCLUSIONS
  Sagittal-plane intersegmental kinematic and kinetic links strongly affected the magnitude and direction of GRF and tibiofemoral forces during the impact phase of single-legged landing. Therefore, improving sagittal-plane landing mechanics is important in reducing harmful magnitudes and directions of impact forces on the anterior cruciate ligament.
authors.affiliation: Sport Medicine and Science Research Laboratory, Department of Health and Sport Management, Osaka University of Health and Sport Sciences, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Shimokochi
authors.affiliation: Sports Medicine Assessment Research and Testing Laboratory, George Mason University, Manassas, VA.
authors.forename: Jatin P
authors.initials: JP
authors.lastname: Ambegaonkar
authors.affiliation: Experimental Biomechanics Laboratory, Lawrence Technological University, Southfield, MI.
authors.forename: Eric G
authors.initials: EG
authors.lastname: Meyer
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000502:physiology*; D000070598:Anterior Cruciate Ligament Injuries / Q000517:prevention & control*; D001696:Biomechanical Phenomena; D018592:Cross-Over Studies; D005260:Female; D005269:Femur / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology; D013314:Stress, Mechanical; D013977:Tibia / Q000502:physiology*; D055815:Young Adult
keywords: anterior cruciate ligament; injury prevention; landing strategy; lower extremity biomechanics; tibial posterior slope