Efficacy of tactile stimulation via vibratory ankle supports and insoles on proprioception and balance in functional ankle instability: an exploratory four-armed randomized trial

Functional ankle instability (FAI) is defined by sensorimotor deficiencies that arise from compromised mechanoreceptor activity after repeated lateral ankle sprains. This study was conducted to compare vibrotactile stimulation delivered via insoles or ankle supports with non-stimulated orthoses for improving proprioception and balance in individuals with FAI. Thirty-two physically active adults with FAI were randomized to an insole, vibratory insole, ankle support, or vibratory ankle support group. Each orthosis was worn daily for two weeks. Joint position sense (JPS), static postural stability (center of pressure velocity), and dynamic balance (6-meter timed hop and Y Balance Tests) were assessed at baseline, post-intervention, and two-week follow-up. The vibratory insole group showed significant improvements in JPS error (-1.72°, p = 0.001, d = 2.81) and 6-meter hop time (-0.73 s, p = 0.003, d = 1.29) at two weeks. Between-group comparisons revealed that the vibratory insole outperformed both the insole ( p = 0.003) and vibratory ankle support ( p = 0.004) in JPS at follow-up. Static postural control during single-leg stance, as measured by COP anteroposterior velocity, improved significantly in the ankle support and vibratory ankle support groups ( p ≤ 0.003). Plantar-targeted vibrotactile stimulation via a vibratory insole effectively enhances proprioceptive acuity and balance in FAI.