Robotic Trainer Helps Paraplegics Sit More Stably

A new study shows how a robotic device can assist and train people with spinal cord injuries (SCIs) to sit more stably by improving their trunk control.

Developed at Columbia University (New York, NY, USA), the Trunk-Support Trainer (TruST) is based on a motorized-cable belt placed around the torso that helps determine the individual postural control limits and sitting workspace area for people with SCI. It also delivers forces on the torso when the user performs upper body movements beyond their postural stability limits while sitting. SCI patients first perform maximal trunk excursions along eight directions, radiating in a star-shape, in order to define their seated postural limits and workspace area (in cm²). TruST is then configured to apply assist-as-needed forces when the trunk moves beyond these postural limits.

For the study, the researchers recruited five subjects with SCI who were examined with a customized postural test that required them to follow a ball with their head and move their trunk as far as possible, without using their hands. The test was repeated in eight cardinal directions, and the researchers used the results to compute the sitting workspace of each individual. TruST was then tailored for each subject to apply personalized assistive force fields on the torso while they performed the same movements again. This time, they were able to expand the sitting workspace around their bodies by an average of about 25%. The study was published on January 6, 2020, in Nature Spinal Cord Series and Cases.

"We designed TruST for people with SCIs who are typically wheelchair users. We found that TruST not only prevents patients from falling, but also maximizes trunk movements beyond patients' postural control, or balance limits,” said senior author Professor Sunil Agrawal, PhD. “The robotic platform will be used to train participants with SCI by challenging them to move their trunk over a larger workspace, with TruST providing assist-as-needed force fields to safely bring the subjects back to their neutral sitting posture. This force field will be adjusted to the needs of the participants over time as they improve their workspace and posture control.”

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