The impact of an underactuated arm exoskeleton on wrist and elbow kinematics during Prioritized Activities of daily living

This study addresses the feasibility of underactuated arm exoskeletons as an alternative solution to the often bulky and heavy exoskeletons which actuate the shoulder with 3 DoF. Specifically, the study investigates how the wrist and elbow joint adapts their kinematics when the shoulder abduction is constrained. Ten healthy participants conducted three different grasping activities of daily living, during natural motion and during constrained shoulder abduction at two fixed angles: the resting position angle and at an angle of 10 ° abduction from the resting position. Motion capture data was collected and used as input for a musculoskeletal computer model adapted to this study. Statistical parametric mapping tools were employed to analyze the joint angles estimated by the model. The results show significant differences within the joint angles when the shoulder abduction is constrained. The wrist flexion angle deviated up to 13.6 ° and the elbow pronation angle decreased by 8.7 ° on average throughout the movement compared to the natural motion during restricted shoulder abduction motion. Thus, the shoulder could be underactuated and the participants could still accomplish the activities of daily living with changes in the wrist and elbow joint kinematic angles.