Influence of Seating Surface Rising Trajectory on the Standing Burden in Stand-Assist Chairs

Abstract

In this study, we fabricated two types of stand-assist chairs with different rising trajectories of the seating surface in order to reduce the burden on the user’s body when standing up from them. Then, we analyzed their resulting burden exerted when performing the upright motion. We experimentally examined the two types of chairs and compared them with an additional ordinary one. We analyzed the joint torque using a digital manikin using motion simulation software and measured the muscle activity through electromyography to evaluate the standing load by focusing on the difference in the movement characteristics between standing and upright motions. The knee joint torque associated with the proposed stand-assist chair was about 50% less than that for the ordinary one when the body was heavily loaded during the standing motion. In addition, in that case, the activity of each muscle (erector spinae muscles, vastus medialis muscle, and vastus lateralis muscle) showed the most significant decrease with the downward-arc stand-assist chair.