# Modification of Hand Muscular Synergies in Stroke Patients After Robot-Aided Rehabilitation
## 4 Discussion  
Seven chronic stroke patients (mean age: \(59.6\pm 12.8\)) were involved in this study. All the involved patients showed an increase in the FM and MP scores between before and after the robot-aided rehabilitation of the hand. The average increase was \(7.3\pm 3.7\) for the FM and \(3.1\pm 2.1\) for the MP. Figure 8: Comparison of the muscular synergies of the sound hand (in green) vs. the impaired hand (in the box) before (red) and after (blue) the rehabilitation treatment with the Gloreha robot for can-grasping. Figure 9: Comparison of the muscular synergies of the sound hand (in green) vs. the impaired hand (in the box) before (red) and after (blue) the rehabilitation treatment with the Gloreha robot for ball-grasping. \begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{2}{c}{**CS**} & \multicolumn{4}{c}{**SI**} \\ \hline  & **H-BR *** & **H-AR *** & **BR-AR *** & **H-BR *** & **H-AR *** & **BR-AR *** \\ \hline P & \(0.87\pm 0.08\) & \(0.94\pm 0.03\) & \(0.92\pm 0.06\) & \(0.91\pm 0.04\) & \(0.95\pm 0.05\) & \(0.92\pm 0.04\) \\ S & \(0.75\pm 0.13\) & \(0.85\pm 0.05\) & \(0.87\pm 0.10\) & \(0.86\pm 0.03\) & \(0.94\pm 0.03\) & \(0.84\pm 0.02\) \\ C & \(0.70\pm 0.22\) & \(0.98\pm 0.01\) & \(0.72\pm 0.19\) & \(0.85\pm 0.04\) & \(0.90\pm 0.02\) & \(0.85\pm 0.03\) \\ B & \(0.65\pm 0.14\) & \(0.87\pm 0.09\) & \(0.76\pm 0.20\) & \(0.89\pm 0.05\) & \(0.96\pm 0.04\) & \(0.93\pm 0.04\) \\ \hline  & \(0.74\pm 0.09\) & \(0.91\pm 0.06\) & \(0.82\pm 0.09\) & \(0.88\pm 0.03\) & \(0.94\pm 0.03\) & \(0.89\pm 0.05\) \\ \hline \end{tabular}
\end{table} 
Table 3: Summary table of comparisons among muscular synergy vectors for each exercise. P = pencil; S = sheet; C = cylinder; B = ball; * denotes statistical significance. Moreover, a similarity among the synergy patterns extracted from the EMG signals is already evident from a visual inspection of the results reported for the representative subject. The monitored patients show a high degree of similarity of the involved synergies, as evident from the comparison reported in Table 3. This also manifests in the comparison between the healthy limb and the injured limb before and after the rehabilitation treatment. These results confirm what has been demonstrated in the state-of-the-art with regard to muscle synergies of the upper limb on chronic stroke patients. More in detail, in the state-of-the-art, a preservation of the normal muscle synergies in the stroke-affected arm of a patient, with a similarity level ranging from 0.89 to 0.98, has been demonstrated [15]. The obtained results aim to extend the results to the hand district and to the robot-mediated rehabilitation treatment district. The increase in CS following rehabilitation treatment can be synonymous with its effectiveness, even if a larger population would be needed. This aspect is also confirmed by the statistical analysis; in fact, the increase in CS is statistically significant in H-BR, H-AR, and BR-AR comparisons (\(p\) = 0.018, 0.012, 0.015 with Wilcoxon paired-sample test, respectively). The comparison BR-AR reveals a high mean value of CS (0.82 \(\pm\) 0.09) with two interesting aspects to be considered in terms of motor performance: (i) each patient tends to maintain the synergistic pattern as almost unchanged even after the rehabilitation treatment, although the clinical results show an improvement in motor performance; (ii) motor performance deficits in chronic stroke subjects are not strictly related to the contribution of the single muscle in movement, but to how these are modulated over time (i.e., the corresponding activation coefficient \(H_{i}(t)\)). Furthermore, the results of the comparisons made with SI for each patient are reported in Table 3. The similarity between the vectors of synergies is good both for the comparisons between the healthy limb and the injured limb before and after the robot-aided rehabilitation (mean SI values: H-BR: 0.88 \(\pm\) 0.03; H-AR: 0.94 \(\pm\) 0.03; BR-AR: 0.89 \(\pm\) 0.05).