## 4 Discussion  
The findings presented in this manuscript provide a thorough investigation of grasping task performance among SCI and stroke patients, with the SRPAS that we developed assisting with each task. All participants in our study had established chronic impaired function of the hands (at least 18 months old) and plateaued during their rehabilitation process. SCI participants had impaired function of both hands with UEMS ranging from 22/50 to 40/50 and one among them demonstrated a complete injury. Similarly, stroke participants had their affected hand's muscle function evaluated with the Oxford scale from 0 to 4+, with one participant being left-side plegic. Due to their lesions, the patients demonstrated varied levels of spasticity of the affected hands, ranging from 1 to 4 in the MAS, further impairing their achievable ROM during hand-related activities and SRPAS-assisted tasks. The tasks involved in our investigation were designed to resemble ADLs [6; 29; 59; 60], such as repeated and intermittent performing of spherical, cylindrical, and lumbrical gripping, using objects such as balls, glass and paper. Our SCI participants' disability was documented through the SCIM questionnaire, where their scores in the self-care category indicated severe to moderate disability [61; 62], ranging from 7 to 16 out of 20. Similarly, the disability of our stroke participants was validated through SIS [63; 64], where their cores in the hand domain ranged from 0% to 70% and their scores in the ADL domain ranged from 37.5% to 57.5%. As a result of their impaired motor function, these individuals would not have been able to complete the activities using their affected hands, without the mechanical assistance provided by the SRPAS. The finger flexion values that we acquired for the index, middle, ring, and pinky fingers demonstrate a stable and consistent grip performance, which was made feasible using pneumatic actuation. The relatively uniform flexion across different fingers emphasizes the necessity of this external mechanical help in allowing coordinated finger motions in order to compensate for the lack of individual motor control and reduced ROM. The piezoelectric pressure and sEMG measurements demonstrate the relevance of pneumatic actuation in grasping performance. The increased pressure values recorded, notably during Events 1 and 2, suggest that the SRPAS was actively aiding the SCI participants' grasp. This increased pressure shows that the actuation delivered the necessary mechanical force, allowing participants to execute a task that would otherwise be impossible for them to achieve unaided. The sEMG data, which correlate to muscle activation, demonstrate  
Figure 26: Spearman correlation of participant data. that, while the patients exerted some muscular activity, the robotic aid took on a significant portion of the effort, as reflected in the low-to-moderate sEMG values in relation to the task's mechanical demands. Figures 14-25 present PCA projections of combined time-domain (flex peak amplitude) and frequency-domain (sEMG/accelerometer dominant frequency, total power) features for each exercise and actuation condition. In all plots, PC1 and PC2 capture the largest and second-largest portions of variance, respectively. Color coding denotes non-actuated, left-actuated, and right-actuated trials, while marker shapes distinguish participants. In the ball-grasping PCA (Figure 14), actuated conditions generally form clusters distinct from non-actuated trials, indicating that pneumatic assistance alters both neuromuscular and kinematic signatures--though separation varies by participant. The glass-grip PCA (Figure 19) shows similar patterns: some participants' actuated data shift clearly along PC axes, while others overlap, reflecting individual grasp strategies. Finally, the paper-grip PCA (Figure 25) again reveals that actuation shifts sensor profiles for certain participants but not others.