The robotic Trunk-Support-Trainer (TruST) to measure and increase postural workspace during sitting in people with spinal cord injury

Study design: Cross-sectional study.

Objectives: To measure and expand the sitting workspace of participants with spinal cord injury (SCI) with the Trunk-Support-Trainer (TruST).

Setting: Columbia University.

Methods: TruST is a motorized-cable belt placed around the torso. Participants performed maximal trunk excursions along eight directions, radiating in a star-shape, to define their seated postural limits and workspace area (cm²). TruST was configured to apply "assist-as-needed" forces when the trunk moved beyond these postural limits. Kinematics were collected to examine trunk control. The clinical features of the sample (n = 5) were documented by neurological injury, dynamometry, the American Spinal Injury Association Impairment Scale, and Spinal Cord Independence Measure-III.

Results: Statistical significance was examined with paired t-tests. TruST successfully recreated the postural limits of participants and expanded their active sitting workspace (Mean: 123.3 ± SE: 42.8 cm², p < 0.05). Furthermore, participants improved their trunk excursions to posterior (Mean: 5.1 ± SE: 0.8 cm, p < 0.01), right (Mean: 3.1 ± SE: 1.1 cm, p < 0.05), and left (Mean: 5.0 ± SE: 1.7 cm, p = 0.05) directions with TruST-force field.

Conclusions: TruST can accurately define and expand the active seated workspace of people with SCI during volitional trunk movements. The capacity of TruST to deliver continuous force-feedback at the user's postural limits opens new frontiers to implement motor learning-based paradigms to retrain functional sitting in people with SCI.