# Three-Dimensional Assessment of Upper Limb Proprioception via a Wearable Exoskeleton  
[PERSON]  
1 Assistive Robotics and Interactive Exosuits (ARIES) Lab, Institute of Computer Engineering (ZITI), University of Heidelberg, 69120 Heidelberg, Germany; [EMAIL_ADDRESS] (E.D. ); [EMAIL_ADDRESS] (L.M. );
2 Department of Informatics, Bioengineering, Robotics, and System Engineering (DIRRIS), University of Genoa, 16145 Genoa, Italy; [EMAIL_ADDRESS] 3 Mechanical Measurements and Microelectronics (M3 Lab) Lab, Engineering Department, University Nicolo Cusano, 00166 Rome, Italy; [EMAIL_ADDRESS] 4 Maersk Mc-Kinney Moller Institute, Faculty of Engineering, University of Southern Denmark (SDU), 5230 Odense, Denmark 4  
[PERSON]  
1 Assistive Robotics and Interactive Exosuits (ARIES) Lab, Institute of Computer Engineering (ZITI), University of Heidelberg, 69120 Heidelberg, Germany; [EMAIL_ADDRESS] (E.D. ); [EMAIL_ADDRESS] (L.M. );
2 Department of Informatics, Bioengineering, Robotics, and System Engineering (DIRRIS), University of Genoa, 16145 Genoa, Italy; [EMAIL_ADDRESS] 3 Mechanical Measurements and Microelectronics (M3 Lab) Lab, Engineering Department, University [PERSON], 00166 Rome, Italy; [EMAIL_ADDRESS] 4 Maersk Mc-Kinney Moller Institute, Faculty of Engineering, University of Southern Denmark (SDU), 5230 Odense, Denmark 4  
[PERSON]  
3 Mechanical Measurements and Microelectronics (M3 Lab) Lab, Engineering Department, University [PERSON], 00166 Rome, Italy; [EMAIL_ADDRESS] 4 Maersk Mc-Kinney Moller Institute, Faculty of Engineering, University of Southern Denmark (SDU), 5230 Odense, Denmark 4  
[PERSON]  
2 Department of Informatics, Bioengineering, Robotics, and System Engineering (DIRRIS), University of Genoa, 16145 Genoa, Italy; [EMAIL_ADDRESS] 3 Mechanical Measurements and Microelectronics (M3 Lab) Lab, Engineering Department, University Nicolo Cusano, 00166 Rome, Italy; [EMAIL_ADDRESS] 4 Maersk Mc-Kinney Moller Institute, Faculty of Engineering, University of Southern Denmark (SDU), 5230 Odense, Denmark 4
In regular clinical practice, proprioceptive impairments receive less attention than motor deficits [10], and are usually quantified through clinical scales (Fugl-Meyer Assessment Scale [11] and Nottingham Sensory Assessment scale [12]), lacking in accuracy, precision, and reliability [13; 14], and leading to incongruences and low agreement with clinical results obtained from imaging studies [10]. Scientific literature reports several attempts to provide quantitative measurements of proprioception [15; 16; 17; 18; 19]: [PERSON] et al. adopted a planar robotic exoskeletal arm to quantify proprioception after stroke in a bidimensional workspace (2D) by means of a classic position matching task paradigm [20; 21]. They passively moved the patients' impaired arm towards a target position, and successively asked them to mirror with the contralateral arm. Results provided evidence that proprioceptive sensitivity depends on both the arm's configuration and the movement direction. Other contributions [22; 23; 24] found that muscle spindles are sensitive to movements in different directions which are highly specific: each muscle shows a maximum sensitivity to a particular movement direction, i.e., the preferred sensory direction. Further studies have shown that the central nervous system programs movements considering the gravity acting on the limb: arm kinematics changes for movements performed across different directions along the \"vertical axis\" (i.e., going upward or downward), coherently with the optimization of both inertial and gravitational forces [25; 26; 27]. Hence, in a three-dimensional workspace, proprioceptive sensitivity could be modulated by gravity's effects on the arm configuration. [PERSON] et al. [28] used a planar robotic arm to analyse proprioceptive acuity in single-joint and multi-joint tasks, focusing on the elbow, shoulder, and hand, still limited to a 2D planar workspace. Only recently, authors started to treat the evaluation of proprioception across a three-dimensional (3D) space: [PERSON] et al.