## 5 Discussion  
In this work we presented a robotic rehabilitation program that has the potential to improve wrist motor control in individuals with MS. Significant decreases in tracking and figural error occurred from pre to post intervention in the trained limb, supporting our first hypothesis related to improvements in wrist motor accuracy. To our knowledge, this was the first study to deliver an adaptive training program to the upper limb in an MS population, offering resistive torques as well as assistance. This adaptive, repetitive, and participant tailored approach has proved beneficial for various types of MS, severity of disease and years since diagnosis. Additionally, results of increased muscular strength at the wrist joint partially supports our second hypothesis. However, no correlations between wrist strength and clinical outcome measures were found. The results of this study identified significant improvements in tracking performance (defined by decreases in tracking and figural error) in the trained limb. The adaptive and repetitive protocol was designed to improve the neuromechanical control of the hand during the tracking task, as indicated by error decreases, improved accuracy, and control \begin{table}
\begin{tabular}{c c c} \hline
**Direction** & \(p\)**-Value** & \(\mathbf{r^{2}}\) \\ \hline Flexion & 0.03 * & 0.64 \\ Extension & 0.02 * & 0.68 \\ Radial Deviation & 0.04 * & 0.59 \\ Ulnar Deviation & 0.08 & 0.49 \\ \hline \end{tabular}  
* Denotes significant differences, \(p\) < 0.05.  
\end{table} 
Table 2: Linear regression correlation between isometric wrist force and tracking error of the trained limb at T1 (mean values). of the trajectory without assistance. Training results (Section 4.1) showed that participants improved their performance across sessions in terms of spatial accuracy (FE), while TE tended to get worse. FE considered only the spatial component of tracking, i.e., the accuracy in replicating the target trajectory, conversely TE considered the differences in speed between target and end-effector. These trends should be investigated further, since they could be either a marker of fatigue or a sign of changed motor strategy, that turned to prefer spatial accuracy. In particular, the latter could have been the successful choice that made participants improve both TE and FE in the last assessment, without forces. Comparing the performance during the assessment sessions (Section 4.2), in absence of assistive/resistive torques, FE reduced by 46%, while TE decreased by 26%. These significant reductions in both figural and tracking error demonstrate improvements in task performance, with a significant reduction in error between the target and the end-effector. This could result from an increase in motor control of the distal upper limb to correctly perform the task without the assistance of the robot. These results align with existing work on robotic rehabilitation of the upper limb for stroke and MS populations that report improvements or demonstrated a reduction in errors from pre-post intervention of reaching and tracing tasks [7,17,19]. Movement accuracy is typically quantified by smoothness of the curvature or the decreasing measure of end-point trajectory post-intervention, as was also demonstrated in our results; these findings indicate that the repetitive and high-dose tracking task improved overall performance of the skill. The combination of wrist movements necessary to complete the figure-eight tracking task were a combination of wrist flexion/extension and radial/ulnar deviation. These movements are a fundamental component in performing many ADLs such as turning a doorknob or twisting a lid off a jar. Improving muscular strength and movement accuracy when performing these basic daily tasks may enhance one's quality of life [26]. Although only the most affected limb underwent the adaptive training protocol, both limbs showed improvements.