Enhancing Seated Postural Coordination in a Virtual Reality Reach Task: Effects of Robotic Pelvic Guidance and Visual Feedback

Individuals with trunk impairments from neurological conditions often struggle with postural coordination, making it difficult to maintain upright sitting and limiting both mobility and rehabilitation. This study introduces a novel seated postural training approach using the pelvic Wheelchair Robot for Active Postural Support (pWRAPS), which delivers active pelvic guidance in a virtual reality (VR) environment to facilitate upper body coordination. We investigated how pelvic guidance, combined with different visual feedback (VF) strategies, influences upper-body coordination during a four-direction hand-tracking game. The goal of this paper is to validate our methods and outcomes in able-bodied subjects. Thirty-two healthy adults were randomly assigned to four groups (eight per group) based on guidance (guided vs. unguided) and visual feedback (control vs. error-based). In the guided condition, pWRAPS actively guided the pelvis during reaching, while in the unguided condition, the robot remained transparent. Control visual feedback showed a moving hand target, whereas error-based visual feedback displayed hand-tracking errors. Participants who received pelvic guidance showed significantly greater improvements in task performance and body segmental coordination than those without guidance, regardless of visual feedback. Error-based visual feedback further influenced trunk-pelvis coordination, regardless of guidance. Additionally, upper trunk coordination was significantly associated with participants' sense of agency (SoA), reflecting their perceived control over the movement. While varying visual feedback across sessions may enhance engagement, combining it with pelvic guidance is key to sustaining effective training outcomes. These findings highlight a promising approach for seated postural rehabilitation, by integrating pWRAPS with virtual reality.