## 2 Materials and Methods
### Experimental Validation
#### 2.4.1 Data Acquisition  
The measurements took place in the Laboratory of Robotics at the Faculty of Electrical Engineering, Ljubljana, Slovenia. The subjects were healthy individuals with no prior acute or chronic injuries that would limit the ROM of their wrist or fingers. The group of participants consisted of six people--four males and two females--mean age 29.5 years \(\pm\) 6.7 years, mean body weight 73 kg \(\pm\) 18 kg, and mean height 178 cm \(\pm\) 12 cm. Anthropometric characteristics of the subjects--weight, height, and hand dimensions--are shown in Table 1.  
In order to reduce the complexity of the measurements, our measurement protocol focused on the wrist, middle (MF), and pinkie (PF) finger--the third and fifth digit--joints. The thumb was not included in the analysis because this device does not actively target \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & **Sex** & **Age/Years** & **Weight/kg** & **Height/cm** & **DA** & \
\begin{tabular}{c} **W-MF** \\ **MCP/cm** \\ \end{tabular} & **W-PF** &
\begin{tabular}{c} **W-PF** \\ **MCP/cm** \\ \end{tabular} & **LMF/cm** & **LPF/cm** & **HW/cm** \\ \hline Subject A & M & 25 & 75 & 194 & R & 10.5 & 9.6 & 11.0 & 7.9 & 8.0 \\ \hline Subject B & M & 27 & 88 & 186 & R & 10.3 & 8.3 & 10.7 & 7.9 & 8.6 \\ \hline Subject C & F & 28 & 60 & 164 & R & 9.4 & 7.4 & 9.6 & 7.2 & 7.8 \\ \hline Subject D & M & 25 & 65 & 174 & R & 9.8 & 8.8 & 11.0 & 8.0 & 8.2 \\ \hline Subject E & F & 27 & 52 & 169 & R & 9.5 & 8.6 & 9.8 & 7.6 & 7.5 \\ \hline Subject F & M & 43 & 100 & 186 & R & 9.8 & 8.8 & 11.0 & 8.0 & 10.0 \\ \hline \hline \end{tabular}  
* DA—dominant arm, where R is the right dominant arm and L is the left dominant arm. W-MF MCP—distance between the wrist and the MF MCP joint; length of the third metacarpal bone. W-PF MCP—distance between the wrist and the PF MCP joint; length of the fifth metacarpal bone. LMF—distance between the MF MCP joint and the MF tip; length of the MF. LPF—distance between the PF MCP joint and the PF tip; length of the PF. HW—hand width, with thumb in opposition.  
\end{table} 
Table 1: Sex, age, dominant arm, and anthropometric properties of the subjects. Figure 6: A block diagram for the resistive mode of operation with all the used hardware and signals. rehabilitation of its function. We chose to focus on the MF and PF because, in most people, MF is the longest; furthermore, it is positioned in the middle of the hand. Therefore, it can be, as such, also a good representation of the movement for the index and ring finger--the second and fourth digit. The PF, by contrast, is usually the shortest finger of the human hand and has its PIP and distal interphalangeal (DIP) joints' axes noticeably misaligned with the other three fingers. We used 11 active infrared light-emitting diode (LED) markers, sampled at 100 Hz--they were placed, posteriorly, on the forearm, ulnar, and radial styloid process, MCP, PIP, DIP joints, and fingertips of the MF and PF. The task for each protocol was described to the subjects, who then performed the three measurement protocols in the same order, for 30 s each:  
* P0 protocol--active movement through the available ROM, spanning from the full coupled flexion of the wrist and fingers to their full extension, with the thumb held in opposition, only using the device's proximal part to have the forearm secured in the splint. The movement speed was optional;
* P1 protocol--active movement through the device's available ROM with a passive device equipped. The movement speed was optional;
* P2 protocol--passive, actuated movement through the device's available ROM, where only the device was actively contributing to the movement. The device was moving through its available ROM so that one cycle of the movement--from flexion into extension and back--lasted five seconds. The 3D movement of the LED markers was captured using three Optotrak Certus NDI (Northern Digital) motion capture systems. According to [52], this motion tracking system has an absolute error of less than 0.1 mm.