Can balance training affect the ankle joint stiffness in subjects with unilateral chronic ankle instability?

Abstract

Background: Lateral ankle sprain is one of the most frequent sports-related injuries, accounting for up to 60% of all athletic injuries. The development of repetitive ankle sprains and persistent residual symptoms such as repeated episodes of ankle giving way, pain, weakness, loss of function, and feeling of ankle instability after injury has been termed chronic ankle instability (CAI). The signs and symptoms of initial injury often resolve with time but mechanical joint laxity may last longer leading to residual symptoms. Balance training has been shown to be effective in preventing ankle sprain recurrences in subjects with CAI but the biomechanical and/or neurophysiological pathways underlying the clinical outcomes are still unknown. Balance training is routinely used in clinical practice for sprained ankles, however to our knowledge, only one study has examined the effects of balance training intervention on flexibility characteristics of the ankle joint in patients with CAI. Purpose: This study was conducted to determine if a 4week 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:Atbaseline, themeanvalues of the inversion stiffness (0.69± 0.37Nm/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± 0.41Nm/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. Conclusion(s): 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. Implications:Traditionally, taping and bracing have been used to improve stability and prevent recurrent ankle injury in patients with CAI. However, the beneficial effects of ankle taping have been attributed to enhanced proprioception and mechanical restriction, but there is no indication of restoring ligamentous stability. Further research with additional stiffness measures along with functional tests, larger sample size, and progressive balance training exercises is needed to identify if the mechanical characteristics of chronic unstable ankles can be altered.