title: Clinical assessment of countermovement jump landing kinematics in early adolescence: Sex differences and normative values.
abstract: BACKGROUND
  Adolescent females have been reported to have a higher risk of non-contact knee joint injuries compared to their male counterparts, with deficiencies in neuromuscular control being purported to be the primary differentiating factor. As such, assessment of movement quality during functional screening tests in this population is warranted. Widespread implementation of such screening requires clinically accessible screening measures and normative data. Therefore, the aim of the present study was to provide normative data for clinical analysis of landing kinematics in early adolescent male and female athletes, with a corollary of determining whether a difference between the sexes is evident with such screening.
  
  
  METHODS
  Ninety seven male and 84 female athletes (mean age=13±1.41years) in the first year of high school participated. Each participant performed 3 countermovement jump trials. Frontal and sagittal plane knee joint angles were recorded by video cameras for both dominant and non-dominant limbs. A multivariate analysis of variance (MANOVA) was used to determine the effect of sex on the dependent variables.
  
  
  RESULTS
  Males displayed significantly greater knee flexion prior to initial contact (P<0.001) and knee varus displacement (P<0.001). No differences were observed between males and females for max knee flexion (P>0.05).
  
  
  CONCLUSIONS
  Early adolescent female athletes demonstrate less desirable landing biomechanics than their male peers. The first year in high school, when early adolescent females are first exposed to high school sports, may be an ideal time to assess movement quality during functional tasks and intervene with injury prevention programs if necessary.
authors.affiliation: School of Public Health, Physiotherapy and Population Science, University College Dublin, Dublin, Ireland. Electronic address: sinead.holden@ucdconnect.ie.
authors.forename: Sinéad
authors.initials: S
authors.lastname: Holden
authors.affiliation: School of Public Health, Physiotherapy and Population Science, University College Dublin, Dublin, Ireland; Institute for Sport and Health, University College Dublin, Dublin, Ireland.
authors.forename: Colin
authors.initials: C
authors.lastname: Boreham
authors.affiliation: School of Public Health, Physiotherapy and Population Science, University College Dublin, Dublin, Ireland.
authors.forename: Cailbhe
authors.initials: C
authors.lastname: Doherty
authors.affiliation: School of Public Health, Physiotherapy and Population Science, University College Dublin, Dublin, Ireland.
authors.forename: Dan
authors.initials: D
authors.lastname: Wang
authors.affiliation: School of Public Health, Physiotherapy and Population Science, University College Dublin, Dublin, Ireland; Institute for Sport and Health, University College Dublin, Dublin, Ireland.
authors.forename: Eamonn
authors.initials: E
authors.lastname: Delahunt
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D009068:Movement; D059385:Plyometric Exercise; D012016:Reference Values; D012307:Risk Factors; D012737:Sex Factors
keywords: 2D analysis; ACL; Adolescence; Biomechanics; Clinical assessment