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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 (cm 2 ). 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 cm 2 , 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.

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In people with severe neuromotor deficits of trunk and lower extremities, regaining balance in standing is often performed in rehabilitation with manual assistance, rigid body supports or by the use of handrails. To investigate and further expand postural control training in standing, we developed a Robotic Upright Stand Trainer (RobUST). In this study, we used RobUST to deliver trunk perturbations while simultaneously providing postural assistive forces on the pelvis in 10 able-bodied adults. Posture control responses with 'pelvic support' was then compared to 'no support' and 'hand supported' standing, with and without assistance from RobUST. We characterize postural imbalance with kinematic displacements and center of pressure (COP) outcomes, such as amplitude and root mean square of the excursions of COP. Surface electromyography (sEMG) was also applied to investigate muscle control. We additionally investigated ground reaction and handrail forces during standing to analyze how postural strategies and muscle mechanisms with 'pelvic support' via RobUST would differ from standing with 'no support' and with the 'handrail support'. Our results show that during perturbations, pelvic assistive support decreased kinematic and COP excursions compared to standing with no support. The pelvic assistance from RobUST showed similar level of COP changes as the use of handrail support but without reducing muscle activity or ground reaction forces. As expected, the maximum level of postural stability was observed when participants used the handrail and received pelvic assistive forces. In conclusion, RobUST demonstrates potential as a training device since it enhances postural balance without