title: Balance training and center-of-pressure location in participants with chronic ankle instability.
abstract: BACKGROUND
  Chronic ankle instability (CAI) occurs in some people after a lateral ankle sprain and often results in residual feelings of instability and episodes of the ankle's giving way. Compared with healthy people, patients with CAI demonstrated poor postural control and used a more anteriorly and laterally positioned center of pressure (COP) during a single-limb static-balance task on a force plate. Balance training is an effective means of altering traditional COP measures; however, whether the overall location of the COP distribution under the foot also changes is unknown.
  
  
  OBJECTIVE
  To determine if the spatial locations of COP data points in participants with CAI change after a 4-week balance-training program.
  
  
  METHODS
  Randomized controlled trial.
  
  
  METHODS
  Laboratory.
  
  
  METHODS
  Thirty-one persons with self-reported CAI.
  
  
  METHODS
  Participants were randomly assigned to a 4-week balance-training program or no balance training.
  
  
  METHODS
  We collected a total of 500 COP data points while participants balanced using a single limb on a force plate during a 10-second trial. The location of each COP data point relative to the geometric center of the foot was determined, and the frequency count in 4 sections (anteromedial, anterolateral, posteromedial, posterolateral) was analyzed for differences between groups.
  
  
  RESULTS
  Overall, COP position in the balance-training group shifted from being more anterior to less anterior in both eyes-open trials (before trial = 319.1 ± 165.4, after trial = 160.5 ± 149.5; P = .006) and eyes-closed trials (before trial = 387.9 ± 123.8, after trial = 189.4 ± 102.9; P < .001). The COP for the group that did not perform balance training remained the same in the eyes-open trials (before trial = 214.1 ± 193.3, after trial = 230.0 ± 176.3; P = .54) and eyes-closed trials (before trial = 326.9 ± 134.3, after trial = 338.2 ± 126.1; P = .69).
  
  
  CONCLUSIONS
  In participants with CAI, the balance-training program shifted the COP location from anterolateral to posterolateral. The program may have repaired some of the damaged sensorimotor system pathways, resulting in a more optimally functioning and less constrained system.
authors.affiliation: University of Virginia, Charlottesville.
authors.forename: Abby
authors.initials: A
authors.lastname: Mettler
authors.forename: Lisa
authors.initials: L
authors.lastname: Chinn
authors.forename: Susan A
authors.initials: SA
authors.lastname: Saliba
authors.forename: Patrick O
authors.initials: PO
authors.lastname: McKeon
authors.forename: Jay
authors.initials: J
authors.lastname: Hertel
mesh_terms: D000704:Analysis of Variance; D000842:Ankle; D016512:Ankle Injuries / Q000150:complications* / Q000503:physiopathology; D000843:Ankle Joint / Q000502:physiology; D002908:Chronic Disease; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology / Q000534:rehabilitation*; D008297:Male; D004856:Postural Balance / Q000502:physiology*; D011312:Pressure; D016059:Range of Motion, Articular; D066191:Sensorimotor Cortex / Q000502:physiology; D016896:Treatment Outcome; D055815:Young Adult
keywords: postural control; rehabilitation; sprains