Robot-mediated physical Human-Human Interaction in Neurorehabilitation: a position paper

TL;DR

This position paper addresses the limited impact of robotics alone in neurorehabilitation by proposing robot-mediated physical Human-Human Interaction (RHHI) that preserves therapist expertise while leveraging robotic strength. It presents a unified taxonomy and a social-psychology–inspired interaction framework to describe RHHI, along with concrete application scenarios across impairment assessment, upper-limb and gait training, sit-to-stand practice, group therapy, and remote rehabilitation. The authors discuss design, control, and networking challenges, emphasize co-creation with clinicians, and outline open research questions on motor learning mechanisms, motivation, partner dynamics, and cost-effectiveness. Overall, RHHI is positioned as a synergistic approach that could enhance clinical outcomes and access, provided rigorous validation, safety, and economic viability are demonstrated through multidisciplinary collaboration and clinical translation.

Abstract

Neurorehabilitation conventionally relies on the interaction between a patient and a physical therapist. Robotic systems can improve and enrich the physical feedback provided to patients after neurological injury, but they under-utilize the adaptability and clinical expertise of trained therapists. In this position paper, we advocate for a novel approach that integrates the therapist's clinical expertise and nuanced decision-making with the strength, accuracy, and repeatability of robotics: Robot-mediated physical Human-Human Interaction. This framework, which enables two individuals to physically interact through robotic devices, has been studied across diverse research groups and has recently emerged as a promising link between conventional manual therapy and rehabilitation robotics, harmonizing the strengths of both approaches. This paper presents the rationale of a multidisciplinary team-including engineers, doctors, and physical therapists-for conducting research that utilizes: a unified taxonomy to describe robot-mediated rehabilitation, a framework of interaction based on social psychology, and a technological approach that makes robotic systems seamless facilitators of natural human-human interaction.

Figures (1)

• Figure 1: Examples of Robot-mediated physical Human-Human Interaction (RHHI) in neurorehabilitation (NR): (A) Two users (typically a patient and a partner such as a therapist, another patient, or a family member, Partner Characteristics) interact through two robots. The Task definition influences the User strategies and their performance. (B) Multiple patients can perform interactive tasks by virtually connecting multiple devices. (C) Therapist and patient interact via two upper-limb exoskeletons. They can assume different roles during the interaction (Interaction Scenario). (D) Robotic devices can be used for learning by demonstration strategies. (E-F) The interaction medium between the two users is modeled using a virtual spring-damper system characterized by therapist and patient stiffness ($K_T, K_P$) and damping ($D_T, D_P$) during bi-directional (E) and uni-directional (F) interaction. The interaction between users can be in joint-space (E) or in task-space (G).