To Reach the Unreachable: Exploring the Potential of VR Hand Redirection for Upper Limb Rehabilitation

TL;DR

This study addresses the challenge of sustaining motivation and effort in upper-limb rehabilitation for motor-impaired individuals by introducing hand redirection in a VR setting. It compares five hand redirection conditions, including a novel Post-offset technique, in a hospital-based within-subject study with 11 participants, measuring training effort and sense of hand ownership. Results show that hand redirection increases effort and motivation without diminishing ownership, with Post-offset delivering the strongest effects on effort and endurance, suggesting potential for long-term VR rehabilitation programs. The work highlights the importance of balancing therapeutic workload with perceptual ownership and calls for longitudinal clinical studies and integration with traditional rehabilitation methods.

Abstract

Rehabilitation therapies are widely employed to assist people with motor impairments in regaining control over their affected body parts. Nevertheless, factors such as fatigue and low self-efficacy can hinder patient compliance during extensive rehabilitation processes. Utilizing hand redirection in virtual reality (VR) enables patients to accomplish seemingly more challenging tasks, thereby bolstering their motivation and confidence. While previous research has investigated user experience and hand redirection among able-bodied people, its effects on motor-impaired people remain unexplored. In this paper, we present a VR rehabilitation application that harnesses hand redirection. Through a user study and semi-structured interviews, we examine the impact of hand redirection on the rehabilitation experiences of people with motor impairments and its potential to enhance their motivation for upper limb rehabilitation. Our findings suggest that patients are not sensitive to hand movement inconsistency, and the majority express interest in incorporating hand redirection into future long-term VR rehabilitation programs.

Figures (3)

• Figure 1: Overview of the study: (A) The participant wears the BURT and the VR headset. BURT helps participants cancel out the burden of gravity on the affected arm. (B) Warm-up for VR Rehabilitation scene with text hint: "Please adjust your hands and body to a comfortable position" (C) The participant performs reaching in VR, corresponding to depth; (D) The participant performs shoulder flexion in VR, corresponding to vertical; (E) The participant performs horizontal abduction in VR, corresponding to horizontal.
• Figure 2: Hand redirection techniques: (A) No hand redirection; (B) Pre-offset: the virtual hand is displaced a fixed offset from the real hand from the beginning to the end of hand motion; (C) Scaling offset: the virtual hand scales the movement of the real hand by a fixed factor; (D) Post-offset: the virtual hand gradually enlarging the movement when the real hand approaches its maximum reach. In all offset conditions, the parameters are set such that the virtual hand offsets the real hand the same distance when the real hand is at the maximum reach of the user.
• Figure 3: The training effort in three movement directions (depth, vertical, and horizontal) with five different hand redirection conditions, including three hand redirection techniques (Pre-offset, Scaling offset, and Post-offset) and two baseline conditions (no hand redirection w/o reduced difficulty).