Effects of sitting trunk training and stand training with epidural stimulation on sitting trunk kinematics in individuals with chronic motor complete spinal cord injury

Spinal cord epidural stimulation (scES) as well as activity-based training have the potential to improve seated postural control in individuals with spinal cord injury (SCI). Past evidence also suggests that stand training could lead to improved postural control outcomes. Hence, we compared the effects of sitting trunk-specific training with scES and trunk-specific plus stand training with scES on trunk kinematics in seated tasks. Sixteen individuals with cervical SCI (Age: 37.1 ± 12.1 yrs; time post-injury: 11.2 ± 8.2 yrs) implanted with a scES unit were randomized into: Voluntary - Vol (Group 1); or Vol and Stand (Group 2). Each group performed two 80-session interventions. Vol intervention comprised tasks to improve seated trunk control. Group 1 crossed over to Vol and Stand in the second intervention. Each individual performed tall-sit, sagittal plane leans, and frontal plane leans with Vol-scES at 3 time-points (Post Implant, Post Int1, and Post Int2). Center of mass of pelvis and trunk were obtained from full-body kinematics. Six postural control outcomes were then computed: anterior-posterior (TAPD) and lateral trunk displacement (TLD), and trunk velocity in all four directions (anterior-TAV, posterior-TPV, left-TLV, and right-TRV). Improved outcomes were defined as decreases in all velocities and displacements in all tasks, except for an increase in displacement in the direction of movement in leaning tasks. In tall-sit, both intervention sets tended to decrease postural control for both groups, except Group 2 had TLV and TRV decreases after the second intervention while TAV decreased following Vol and Stand training for both groups. In sagittal plane lean, TAV and TPV tended to decrease for Group 1 after Vol and Stand training suggesting that stand training may have supplemented postural control improvements. For Group 2, TAV tended to decrease after the first intervention and TAPD increased after both intervention sets. In frontal plane lean, all velocities and TAPD tended to decrease for Group 1 after Vol only training while only TAV, and TRV improved after Vol and Stand training, suggesting that added stand training had a limited effect on lateral control. For Group 2, TAV, and TPV tended to decrease after the first intervention, while TLV, and TRV tended to decrease after the second intervention. The addition of stand training post voluntary training tended to have a greater effect on postural control in sagittal plane lean task, while both groups showed similar improvements in frontal plane lean. These results further our understanding of task-specificity during training interventions and aid in developing better rehabilitation protocols.