Effects of High-definition Transcranial Direct Current Stimulation on Foot Muscle Strength,Ankle Kinesthesia,and Static Balance

To investigate the effects of a single-session high-definition transcranial direct current stimulation(HD-tDCS) on foot muscle strength, ankle kinesthesia, and static balance. In this double-blinded sham-controlled study, 14 healthy young male college students completed two trials with a 20-minute session of tDCS targeting the sensorimotor cortex or a sham stimulation,respectively. Two-way ANOVA with repeated measures was used to analyze the effects of tDCS on the flexor strength of toes, the threshold of ankle passive kinesthesia, and static balance. All participants completed the experiments with no unexpected side effects or adverse events. The total correct rate of subjective guesses was 35.7%, which showed the blinding protocol was acceptable.Compared to pre-tDCS, a significant increase of the flexor strength of first toe(P<0.05), and decrease in the ankle varus passive kinesthesia(P<0.05) was observed after real tDCS, while no significant changes were observed after sham. Additionally, the anteroposterior and medio-lateral sway velocity of the center of gravity was significantly decreased in single-leg standing with closed eyes after real tDCS and sham(P<0.05). This study demonstrated that HD-tDCS can improve the flexor strength of the toes and reduce the ankle passive kinesthesia threshold immediately, and then improve the single-leg standing balance with closed eyes. It was suggested that the non-invasive brain stimulation technology may serve as a novel strategy to enhance foot muscle strength, foot perception function and static balance ability in daily training for foot core.