title: Dynamic postural stability deficits in subjects with self-reported ankle instability.
abstract: OBJECTIVE
  A limited understanding of how functional ankle instability (FAI) affects dynamic postural stability exists because of a lack of reliable and valid measures. Therefore, the purpose of this investigation was to determine whether a new reliable index for dynamic postural stability could differentiate between those with stable ankles and those with FAI.
  
  
  METHODS
  Data were collected on 108 subjects (54 subjects with stable ankles (STABLE group); 54 subjects with functionally unstable ankles (FAI group)). Subjects performed a single-leg-hop stabilization maneuver in which they stood 70 cm from the center of a force plate, jumped off both legs, touched a designated marker placed at a height equivalent to 50% of their maximum vertical leap, and landed on a single leg. The dynamic postural stability index and directional stability indices (medial/lateral, anterior/posterior, and vertical) were calculated. The raw and normalized (to energy dissipated) indices were compared between groups.
  
  
  RESULTS
  Significant differences were noted for the anterior/posterior stability index (FAI = 0.36 +/- 0.09, STABLE = 0.30 +/- 0.06). Similar results were seen for the vertical stability index (FAI = 0.73 +/- 0.17, STABLE = 0.61 +/- 0.13), the normalized dynamic postural stability index (FAI = 0.85 +/- 0.17, STABLE = 0.73 +/- 0.12), the normalized vertical stability index (FAI = 0.007 +/- 0.004, STABLE = 0.005 +/- 0.001), and the dynamic postural stability index (FAI = 0.008 +/- 0.003, STABLE = 0.006 +/- 0.001).
  
  
  CONCLUSIONS
  These results indicate that the dynamic postural stability index is a sensitive measure of dynamic postural stability and is capable of detecting differences between individuals with stable ankles and individuals with functionally unstable ankles.
authors.affiliation: Center for Exercise Science, University of Florida, Gainesville, FL 32611-8205, USA. ewikstrom@hhp.ufl.edu
authors.forename: Erik A
authors.initials: EA
authors.lastname: Wikstrom
authors.forename: Mark D
authors.initials: MD
authors.lastname: Tillman
authors.forename: Terese L
authors.initials: TL
authors.lastname: Chmielewski
authors.forename: James H
authors.initials: JH
authors.lastname: Cauraugh
authors.forename: Paul A
authors.initials: PA
authors.lastname: Borsa
mesh_terms: D000328:Adult; D016512:Ankle Injuries / Q000209:etiology*; D000843:Ankle Joint; D001265:Athletic Injuries / Q000209:etiology*; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D008297:Male; D009068:Movement / Q000502:physiology*; D010465:Perception; D004856:Postural Balance; D011187:Posture / Q000502:physiology*; D016059:Range of Motion, Articular; D012189:Retrospective Studies