The Retrainer Light-Weight Arm Exoskeleton: Effect of Adjustable Gravity Compensation on Muscle Activations and Forces

Abstract

The recovery of voluntary arm movements is one of the most important goals during stroke rehabilitation in order to avoid long-term disability in activities of daily living. Support against gravity in order to reduce flexion synergy is reported as an effective strategy to enable upper extremity rehabilitation. In this study, the reduction of muscle activities and muscle forces with the gravity compensated RETRAINER upper limb exoskeleton were analyzed carrying out defined movements with healthy subjects. The EMG signals of the main active muscles as well as the kinematics of different defined motions were captured and compared. The joint kinematics and the joint moments were computationally determined using a 3D musculoskeletal model. The effectiveness of the upper limb gravity compensation could be shown in both mean values of EMG signals and resulting muscle forces, indicating that this compact and lightweight arm exoskeleton can serve as a powerful tool to support the rehabilitation process.