title: Kinematics and electromyography of landing preparation in vertical stop-jump: risks for noncontact anterior cruciate ligament injury.
abstract: BACKGROUND
  Biomechanical analysis of stop-jump tasks has demonstrated gender differences during landing and a potential increase in risk of noncontact anterior cruciate ligament injury for female athletes. Analysis of landing preparation could advance our understanding of neuromuscular control in movement patterns and be applied to the development of prevention strategies for noncontact anterior cruciate ligament injury.
  
  
  OBJECTIVE
  There are differences in the lower extremity joint angles and electromyography of male and female recreational athletes during the landing preparation of a stop-jump task.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Three-dimensional videographic and electromyographic data were collected for 36 recreational athletes (17 men and 19 women) performing vertical stop-jump tasks. Knee and hip angular motion patterns were determined during the flight phase before landing.
  
  
  RESULTS
  Knee and hip motion patterns and quadriceps and hamstring activation patterns exhibited significant gender differences. Female subjects generally exhibited decreased knee flexion (P = .001), hip flexion (P = .001), hip abduction (P = .001), and hip external rotation (P = .03); increased knee internal rotation (P = .001); and increased quadriceps activation (P = .001) compared with male subjects. Female subjects also exhibited increased hamstring activation before landing but a trend of decreased hamstring activation after landing compared with male subjects (P = .001).
  
  
  CONCLUSIONS
  Lower extremity motion patterns during landing of the stop-jump task are preprogrammed before landing. Female subjects prepared for landing with decreased hip and knee flexion at landing, increased quadriceps activation, and decreased hamstring activation, which may result in increased anterior cruciate ligament loading during the landing of the stop-jump task and the risk for noncontact ACL injury.
authors.affiliation: Department of Orthopedic Surgery, University of North Carolina, Chapel Hill, NC 27599-7135, USA.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Chappell
authors.forename: R Alexander
authors.initials: RA
authors.lastname: Creighton
authors.forename: Carol
authors.initials: C
authors.lastname: Giuliani
authors.forename: Bing
authors.initials: B
authors.lastname: Yu
authors.forename: William E
authors.initials: WE
authors.lastname: Garrett
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000502:physiology*; D000070598:Anterior Cruciate Ligament Injuries; D001265:Athletic Injuries / Q000209:etiology / Q000503:physiopathology; D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D018570:Risk Assessment; D012737:Sex Factors; D013647:Task Performance and Analysis