## 7 Discussion
Conversely, gross motor skills can be evaluated using the larger workspace provided by the robotic arm, since in this layout, the drawing task is more similar to painting a wall, which requires the coordination of larger muscle masses. Note that if the patient interacts with the robot while standing, the drawing execution would require the coordination of more body joints. Other studies have also tried to increase the workspace range to allow measuring gross motor coordination by promoting tasks in larger workspaces [34,35]. However, advances in force-control techniques in robotics open new opportunities in the assessment and rehabilitation of EHC due to the programming versatility of robotic devices. In order to validate the feasibility of the proposed multimodal framework, particularly the robot-based system, preliminary experiments were carried out with healthy volunteers in the laboratory. On one hand, the results show that the proposed system allows for storing the position trajectory of the player ball in the video game (which is directly related to the hand movements of patients) with a sufficient frequency to reproduce the hand movements. This position information can be directly related to the hand movements of patients and used to analyse the motion quality. The analysis of endpoint trajectories is a common approach employed in similar studies [7; 17; 32]. On the other hand, using a larger robotic device does not affect the expected gameplay, since all the participants had no problems performing the drawing tasks. For this experiment, the robot was operating in gravity compensation mode, reducing the resistance to motion. However, more force control-based strategies can be explored using the robotic arm, including different resistance levels to make it harder or easier for the patient to move the end-effector, even incorporating the assistance-as-needed approach. These preliminary results are useful in preparing for pilot trials with patients with UL motor problems. Furthermore, this paper presents a method for trajectory comparison using the DTW algorithm, showing that it is possible to detect differences between right- and left-handed participants or dominant versus non-dominant hands. The poorer performance, marked by higher DTW values for traces developed with the non-dominant hand, suggests that this multimodal system is feasible for measuring motor skills. Furthermore, the DTW values also show that performance in drawing tasks involving large movements is different. Figure 11 shows that higher DTW values were obtained for the robot-based system, clearly distinguishing between fine and gross motor performances. These results agree with the findings of [PERSON] et al. [54], who investigated the relationship between fine and gross motor coordination tasks through a network analysis linking graphomotor tasks (using tablet PC tracing), gross coordination (using items from the Korperkoordinationsstef fur Kinder), and strength (measured by handgrip) in school children. Their results suggest that specific parameters of tracing tasks, as well as other graphomotor tasks, should be taken into account when evaluating developmental trajectories and dysfunctions. As a final remark, most of the methods for assessing motor coordination are based on performance levels during point-to-point movements (endpoint trajectory). However, these endpoint trajectories can be achieved through an infinite number of joint configurations (degrees of freedom [DoFs]), providing abundant movement patterns to accomplish the same motor task [55]. The \"principle of abundance\" implies that the numerous DoFs allow the system to adapt movements to changing environmental conditions, which often occur during the performance of ADL [36]. Therefore, measuring interjoint coordination in relation to motor abundance and task-specific variability is important for understanding reaching deficits [36]. This highlights the need to develop more accurate assessment systems that can identify different levels of motor coordination.