title: Movement variability during single leg jump landings in individuals with and without chronic ankle instability.
abstract: BACKGROUND
  Repeated episodes of giving way at the ankle may be related to alterations in movement variability.
  
  
  METHODS
  Eighty-eight recreational athletes (39 males, 49 females) were placed in 4 groups: mechanically unstable, functionally unstable, copers, and controls based on ankle injury history, episodes of giving way, and joint laxity. Lower extremity kinematics and ground reaction forces were measured during single leg landings from a 50% maximum vertical jump in the anterior, lateral, and medial directions. Ensemble curves of 10 trials were averaged and coefficients of variation were identified for ankle, knee, hip, and trunk motion in 3 planes. A log(e) (ln) transformation was performed on the data. Mixed model analyses of variance (ANOVAs) with Tukey post-hoc tests were utilized with Bonferroni corrections to α ≤ 0.008.
  
  
  RESULTS
  At the knee, controls were more variable than functionally unstable and copers for knee rotation before initial contact, and were more variable during stance than functionally unstable in knee rotation (P ≤ 0.008). Interactions during stance revealed controls were more variable than functionally unstable in lateral jumps for hip flexion, and than mechanically and functionally unstable in hip abduction in the anterior direction (P≤0.008). Controls were more variable than all other groups in hip flexion and than mechanically unstable in hip abduction (P ≤0 .008).
  
  
  CONCLUSIONS
  Individuals with ankle instability demonstrated less variability at the hip and knee compared to controls during single leg jump landings. Inability to effectively utilize proximal joints to perform landing strategies may influence episodes of instability.
authors.affiliation: Department of Kinesiology Biomechanics Laboratory, University of Georgia, USA. browncn@uga.edu
authors.forename: Cathleen
authors.initials: C
authors.lastname: Brown
authors.forename: Bradley
authors.initials: B
authors.lastname: Bowser
authors.forename: Kathy J
authors.initials: KJ
authors.lastname: Simpson
mesh_terms: D000293:Adolescent; D000843:Ankle Joint / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D008297:Male; D009068:Movement; D016059:Range of Motion, Articular; D013314:Stress, Mechanical; D013647:Task Performance and Analysis; D055815:Young Adult