## 2 Materials and Methods  
### Experimental Study  
Kinematic and muscle-activation data were collected while participants performed both the real Box and Block test and its virtual version, as used in previous works [8; 10]. The study involved nine healthy participants and four neurologically affected participants with SCI (hereafter referred to as patients) who were recruited from the National Hospital for Paraplegics in Toledo (Spain) [8; 10; 18; 19]. All participants provided informed consent. The study received ethical approval from the local Ethics Committee from Complejo Hospitalario Toledo (No. 372, Date: 30 April 2019) and from the Human Research Ethics Committee from the Universitat Jaume I (CEISH; reference number: CD/27/2022). Specific informed consent was obtained for open-access publication of photographs that could allow participant identification. SCI patients were recruited by hospital clinicians. Healthy participants were recruited from university and hospital staff and students. Four patients with cervical SCI and UE motor function impairment participated in the study. All patients had an injury at a metameric level between C4 and C8, with an American Spinal Injury Association Impairment Scale (AIS) grade ranging from A to D as defined by the International Standards for the Neurological Classification of Spinal Cord injury [20], which was specifically assessed through the upper limb motor score of the right arm (UER) and the Spinal Cord Independence Measure scale (SCIM). Exclusion criteria of patients included vertebral deformities, joint restrictions, prior upper limb surgery, balance disorders, dysmetria due to associated neurologic or orthopaedic disorders, or visual acuity defects. The UER and the SCIM scale were obtained through an assessment conducted by the clinical staff, evaluating the strength of five muscle groups of the dominant UE. Each muscle group was rated on a scale from 0 (no function) to 5 (normal function), with a total possible score of 25 points. For healthy participants, the inclusion criteria required right-handedness and no history of neuromuscular problems or upper arm injuries. Only right-handed participants were included to minimize variability in motor performance due to limb dominance. The demographic characteristics of the sample analysed are provided in Table 1. \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Variables**} & \multicolumn{3}{c}{**Sample Analysed**} \\ \cline{2-3}  & **Healthy (\(n=9\))** & **SCI Patients (\(n=4\))** \\ \hline Sex (Male) * & 1 (11.11\%) & 4 (100.00\%) \\ \hline Age (Years) + & 33.33 \(\pm\) 13.12 & 34.75 \(\pm\) 13.07 \\ \hline Etiology Injury (Traumatic) & - & 4 (100\%) \\ \hline Time Since Injury (Months) & - & 7.50 \(\pm\) 3.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Demographics and functional characteristics of the study sample. All participants were positioned in front of a height-adjustable table. Healthy participants sat on a chair facing the table, while patients sat in their wheelchairs. An electromagnetic Micro Sensor 1.8 of the Viper motion-tracking system (Polhemus, Colchester, VT, USA), sampling at 100 Hz, was placed on the back of the hand to capture its trajectory using the x, y, z Cartesian coordinates of the microsensor relative to the Polhemus Source origin (Figure 1). A CyberGlove (Cyberglove Systems LLC; San Jose, CA, USA), sampling at 100 Hz, was placed on their right hand to measure 16 hand joint angles following a previously validated protocol [21]. Additionally, seven LX230 integral dry reusable surface electromyography (sEMG) wireless electrodes (Biometrics Ltd., Newport, UK), sampling at 1000 Hz, were placed on the forearm. The electrodes were secured with double-sided die-cut tapes (T350; Vicon Motion Systems Ltd., Oxford, UK) at seven locations selected to capture representative muscle activation during daily activities, as outlined in a previous study [22].