Training Seated Postural Coordination in a Virtual Reality Reaching Game by Active Pelvic Guidance from a Robotic Exoskeleton

Individuals with neurological impairments and deficits in trunk control have difficulty maintaining and controlling upright postures during static or dynamic sitting. Passive devices may support the trunk in a wheelchair at the expense of the user's mobility, but opportunities for postural rehabilitation training may be compromised as a result. This paper presents novel seated postural training using a pelvic Wheelchair Robot for Active Postural Supports (pWRAPS) to improve upper body coordination. These tasks are performed within the pelvic range of motion (ROM) in a Virtual Reality (VR) environment. We investigated the effects of active pelvic guidance on upper body coordination during reaching tasks in different directions. Sixteen able-bodied young adult volunteers were assigned to two groups (eight per group). The first group completed the VR task in transparent mode, i.e., without pWRAPS actively guiding the pelvis. The second group completed the same task while their pelvis was actively guided by pWRAPS. The results support our hypothesis that the group with active pelvic guidance is able to adjust their pelvic trajectory closer to the assigned target than the control group without active pWRAPS. Moreover, after training, the group with active pelvic guidance exhibits better hand-tracking and pelvic accuracy than the control group. This indicates that the actively guided subjects simultaneously adjust their upper body and pelvis movements towards their targeted trajectories. This new training approach can potentially be adapted to postural rehabilitation for wheelchair users with limited trunk control.