## 2 Materials and Methods
### Experimental Case Study  
#### 2.2.1 Experimental Procedure  
Tests had carried out in the \"X-in the Loop Simulation Lab\" (XiLab) at the University of Modena and Reggio Emilia. Participants in the experiment received informed consent prior to accessing the lab to take part in the test. A total of 6 subjects i.e., 2 females (age: median 31 years, IQR 5.0 years; height: median 1.68 m, IQR 0.005 m; mass: median 69 kg, IQR 13.5 kg; BMI: median 24.74 kg/m\({}^{2}\), IQR \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Angles**} & \multicolumn{2}{c}{**Considered Keypoints**} & \multicolumn{2}{c}{**Camera View**} \\ \cline{2-5}  & **Left** & **Right** & **Frontal** & **Lateral** \\ \hline Neck flexion/extension & 17-1-11 & 16-1-8 & & X \\ Shoulder abduction & 11-5-6 & 8-2-3 & X & \\ Shoulder flexion/extension & 11-5-6 & 8-2-3 & & X \\ Elbow flexion/extension angle & 5-6-7 & 2-3-4 & X & X \\ Trunk flexion/extension & 1-11-12 & 1-8-9 & & X \\ Knee bending angle & 11-12-13 & 8-9-10 & & X \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Body key points and camera views considered in the computation of the angles. 4.78 kg/m\({}^{2}\)) and 4 males (age: median 30 years, IQR 4.0 years; height: median 1.86 m, IQR 0.0035 m; mass: median 78 kg, IQR 9.0 kg; BMI: median 22.31 kg/m\({}^{2}\), IQR 1.90 kg/m\({}^{2}\)), were involved and asked to pose for five seconds, while recording by the two systems, in the following five different postures (chosen because they are very frequent in standard working procedures or ergonomic assessment research works), in the following order:  
* T-pose: the subjects have to stand straight up, with their feet placed symmetrically and feet slightly apart and with their arms fully extended. * Seated: subjects have to sit on a stool 70 cm in height, with the back straight, hands leaned on the knees, and feet on the floor. * Standing Relaxed: the subjects have to stand comfortably facing straight ahead, with their feet placed symmetrically and feet slightly apart. * Reach: the subjects must stand straight, feet well apart and with the arms stretched forward, simulating the act of grasping an object placed above their head. * Pick up: the subjects have to pick up a box (dimensions 30.5 cm \(\times\) 21 cm \(\times\) 10.5 cm, weight 5 kg) from the floor, and raise it in front of them, keeping it at pelvic level. An example of the analyzed postures can be found in Figure 3.  
Participants' postures were tracked using a Vicon Nexus system powered by 9 Vicon Bonita 10 optical cameras. Cameras were distributed in the space in the most symmetrical configuration possible (Figure 4) to cover the entire working volume. Participants had to stay in the middle of the system acquisition space. They were equipped with a total of 35 reflective markers, positioned on the whole body according to PlugInGait Full Body model specification defined in the Vicon PlugInGait documentation (Figure 5). Vicon Nexus session has been performed on a Dell Precision T1650 workstation with an Intel(R) Xeon(R) CPU E3-1290 V2 at 3.70 GHz, 4 Core(s), with 32 GB RAM, and an NVIDIA Quadro 2000 GPU, running Windows 10 Pro. System calibration was carried out at the beginning of the experiment. Before starting the experiment, PluginGait (PiG) biomechanical models have been defined for the subjects (i.e., one for each) according to their anthropometric parameters. The video capturing for the RGB-MAS was carried out by two Logitech BRIO 4K Ultra HD USB cameras, with a setting video streaming/recording configuration of 1080 p and 30 fps and a 52 vertical and 82 horizontal degree field of view. They were placed at 1.2 m high from the ground (the pelvis height of the subjects) and angled 90 degrees to each other. Both cameras were mounted on tripods to ensure stability. The system works regardless of the subject's position in the camera's field of view, but the cropped image of the subject must consist of a sufficient number of pixels. This depends on the characteristics of the camera used (e.g., resolution, focal length).