Standing Balance Improved by Electrical Muscle Stimulation to Popliteus Muscles

Abstract

Fall prevention is extremely important when it comes to ensuring the well-being of an aging population. There are currently two main fall prevention strategies: wearing exoskeletons to assist with postural stability and using electrical muscle stimulation (EMS) for training the lower limb muscles. However, the former has issues regarding size and weight, and the latter does not have immediate improvement effects. In this paper, we propose a small and lightweight EMS-based system that immediately improves standing balance by applying EMS to the popliteus muscles behind the knees, which leads to unlocking and bending the knees. Bending the knees lowers the center of mass of the human body and stabilizes the standing balance against unexpected perturbations. We conducted a user study with 20 participants to evaluate the proposed system and found that the postural sway decreased significantly more when EMS was applied within 200 ms after perturbation occurrence compared to when no EMS was applied.