Combining transcutaneous interferential-current for nerve inhibition with a robotic assistant device for increasing...

A kilohertz-frequency alternating current transcutaneously applied was introduced as a novel neuromodulation technology for nerve inhibition innervating antagonist muscles. Combining this electrical nerve inhibition with a robotic assistance device has been proposed but not investigated.

This study aimed to demonstrate the effect of combining electrical nerve inhibition with a wearable robotic device on increasing ankle dorsiflexion during walking. We hypothesized that the wearable robotic device would elicit a greater ankle dorsiflexion angle with the same force in walking by applying the transcutaneous interferential-current nerve inhibition (TINI) technique to the tibial nerve.

Eleven healthy young adults performed three experimental conditions. The ankle assistance (AA) condition was walking while wearing an ankle device with operating dorsiflexion assistance during pre-swing and swing phases. For the ankle assistance with electrical stimulation (AE) condition, TINI on the tibial nerve was additionally applied from the AA condition. In the ankle non-assistance (AN) condition, participants wore the device, but assistance was not provided. The joint angles during walking were measured and digitized through a motion analysis system.

During a gait cycle, immediate changes in ankle joint motions were observed in the sagittal plane. In the pre-swing phase, ankle dorsiflexion angle was significantly greater in AE condition than AA and AN. There was no significant difference in joint angle between AA and AN.

This study demonstrates the effectiveness of combining TINI with a wearable robotic ankle device in increasing dorsiflexion angle during the pre-swing phase. This finding provides the feasibility of using TINI as a neuromodulation technique for assisting functional movement in human walking.