Transcranial Direct Current Stimulation Combined With Balance Training for Chronic Ankle Instability: A Double-Blind,...

Transcranial direct current stimulation (tDCS) can enhance cortical activity and improve motor performance, potentially inducing synergetic effects when coupled with balance training. Yet, its effects during balance training in individuals with chronic ankle instability (CAI) remain unclear. This study aimed to evaluate whether tDCS has additive effects on static postural control, neural excitability, and perceived ankle function in individuals with CAI compared with sham stimulation.

Double-blind, pilot randomized controlled trial.

Nineteen individuals with CAI were included. Participants were randomized to either active tDCS or sham tDCS. Participants and experimenters were blinded to group allocation. Twenty minutes of anodal tDCS (2 mA) was applied over the contralateral motor cortex of the CAI-injured side during balance training, 3 times a week for 4 weeks. The primary outcome was static postural control, assessed by center of pressure velocity and area during unipedal stance with eyes open and closed. Secondary outcomes included corticospinal and spinal reflexive excitability (soleus, fibularis longus, and tibialis anterior), evaluated via transcranial magnetic stimulation and Hoffmann reflex methods, respectively, during unipedal stance. Self-reported outcomes were assessed. All outcomes were assessed at baseline, during, and following a 4-week intervention. Individual analyses were conducted.

Individual analyses show changes in static balance, soleus corticospinal excitability, and ankle function over time, regardless of tDCS group. Effect size estimates indicated small group differences at weeks 2 and 4 in the active-tDCS group compared with sham for most measures. However, the center of pressure area under the eyes-closed condition and fibularis longus corticospinal excitability demonstrated potential moderate (d = -0.62) and large (d = -0.88) effects, respectively.

This pilot study indicates that tDCS applied during balance training appears to provide no added benefit. However, potential changes in selected outcomes (center of pressure area and corticospinal excitability) warrant a larger clinical trial.