title: Associations between lower limb muscle activation strategies and resultant multi-planar knee kinetics during single leg landings.
abstract: OBJECTIVE
  Anterior cruciate ligament injury prevention programs purportedly improve knee joint loading through beneficial modification of lower limb neuromuscular control strategies and joint biomechanics, but little is known about how these factors relate during single-legged landings. Thus, we examined the relationship between explicit lower limb muscular pre-activity patterns and knee joint biomechanics elicited during such landings.
  
  
  METHODS
  Randomized controlled trial.
  
  
  METHODS
  Thirty-five female athletes had 3D knee joint biomechanics and lower limb EMG data recorded during a series of single-leg landings. Regression analysis assessed the relationship between pre-activity of vastus lateralis, lateral hamstring and rectus femoris with peak knee flexion angle and moment, and external anterior tibial shear force. Vastus lateralis, lateral hamstring and vastus lateralis:lateral hasmtring co-contraction assessed the relationship with knee abduction angle and moment.
  
  
  RESULTS
  Greater pre-activity of rectus femoris predicted increased peak anterior tibial shear force (R(2)=0.235, b=2.41 and P=0.003) and reduced knee flexion moment (R(2)=0.131, b=-0.591, and P=0.032), while greater lateral hamstring predicted decreased peak knee flexion angle (R(2)=0.113, b=8.96 and P=0.048). No EMG pre-activity parameters were predictors (P>0.05) for knee abduction angle and moment.
  
  
  CONCLUSIONS
  Current outcomes suggest reducing reliance on quadriceps activation may be beneficial during single-legged landings. It also, however, may be required for adequate joint stability during such maneuvers. Further research is needed to determine if inadequate hamstring activation, rather than elevated quadriceps activation, leads to hazardous loading during single-legged landings.
authors.affiliation: School of Kinesiology, The University of Michigan, Ann Arbor, MI, USA. Electronic address: tynbrown@umich.edu.
authors.forename: T N
authors.initials: TN
authors.lastname: Brown
authors.affiliation: School of Kinesiology, The University of Michigan, Ann Arbor, MI, USA.
authors.forename: S G
authors.initials: SG
authors.lastname: McLean
authors.affiliation: School of Kinesiology, The University of Michigan, Ann Arbor, MI, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Palmieri-Smith
mesh_terms: D000293:Adolescent; D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000502:physiology*; D035002:Lower Extremity / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D052097:Quadriceps Muscle / Q000502:physiology; D012399:Rotation; D013977:Tibia / Q000502:physiology; D014741:Video Recording
keywords: Biomechanics; EMG; Knee; Muscle activation; Neuromechanics