title: Four Weeks of Balance Training does not Affect Ankle Joint Stiffness in Subjects with Unilateral Chronic Ankle Instability.
abstract: BACKGROUND
  Balance training has been shown to be effective in preventing ankle sprain recurrences in subjects with chronic ankle instability (CAI) but the biomechanical pathways underlying the clinical outcomes are still unknown. This study was conducted to determine if a 4-week balance training intervention can alter the mechanical characteristics in ankles with CAI.
  
  
  METHODS
  Twenty-two recreationally active subjects with unilateral CAI were randomized to either a control (n = 11, 35.1 ± 9.3 years) or intervention (n = 11, 33.5 ± 6.6 years) group. Subjects in the intervention group were trained on the affected limb with static and dynamic components using a Biodex balance stability system for 4-weeks. The ankle joint stiffness and neutral zone in inversion and eversion directions on the involved and uninvolved limbs was measured at baseline and post-intervention using a dynamometer.
  
  
  RESULTS
  At baseline, the mean values of the inversion stiffness (0.69 ± 0.37 Nm/degree) in the involved ankle was significantly lower (p< 0.011, 95% CI [0.563, 0.544]) than that of uninvolved contralateral ankle (0.99 ± 0.41 Nm/degree). With the available sample size, the eversion stiffness, inversion neutral zone, and eversion neutral zone were not found to be significantly different between the involved and uninvolved contralateral ankles. The 4-week balance training intervention failed to show any significant effect on the passive ankle stiffness and neutral zones in inversion and eversion.
  
  
  CONCLUSIONS
  Decreased inversion stiffness in the involved chronic unstable ankle was found that of uninvolved contralateral ankle. The 4-week balance training program intervention was ineffective in altering the mechanical characteristics of ankles with CAI.
  
  
  METHODS
  Randomized controlled clinical trial; Level of evidence, 1.
authors.affiliation: Department of Physical Therapy and Athletic Training, Northern Arizona University, USA.
authors.forename: Tarang Kumar
authors.initials: TK
authors.lastname: Jain
authors.affiliation: Bioengineering Graduate Program, University of Kansas, Lawrence, USA.
authors.forename: Clayton N
authors.initials: CN
authors.lastname: Wauneka
authors.affiliation: Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, USA.
authors.forename: Wen
authors.initials: W
authors.lastname: Liu
keywords: Ankle instability; Ankle joint laxity; Ankle sprains; Rehabilitation