## 2 Materials and Methods
### Post-Stroke Participants
#### 3.2.3 Paper Grip  
In the paper grip exercise, participants used their fingers as visualized in Figure 20 to lift and hold two cardboard papers. We ran this under three conditions--no actuation, left-side SRPAS assistance, and right-side assistance--to explore how the device influences the performance of this grip. From each trial, we extracted time-domain measures and frequency-domain descriptors. A PCA of these features then revealed clear grouping of sensor responses by condition, highlighting how actuation assists the hand coordination in this grip. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Participant** & **Condition** & **LH EMG Dominant** & **LH EKG Total** & **RH EMG Dominant** & **RH EMG Total** \\  & & **Freq (Hz)** & **Power (\(V^{2}\))** & **Freq (Hz)** & **Power (\(V^{2}\))** \\ \hline HER-01-001 & Non-actuated & 0.099562 & 1878.102515 & 0.099562 & 1888.174548 \\ HER-01-001 & Left Actuation & 0.398248 & 1890.988507 & 0.099562 & 1887.806243 \\ HER-01-001 & Right Actuation & 0.099960 & 1830.000000 & 0.299880 & 1830.000000 \\ HER-02-001 & Non-actuated & 0.100180 & 1890.451842 & 0.400721 & 1890.495245 \\ HER-02-001 & Left Actuation & 0.302419 & 1889.718931 & 0.302419 & 1862.682196 \\ HER-02-001 & Right Actuation & 0.199124 & 1890.608011 & 0.497810 & 1887.605027 \\ HER-02-002 & Non-actuated & 0.100180 & 1889.471475 & 0.500902 & 1890.800619 \\ HER-02-002 & Left Actuation & 0.099562 & 1890.057772 & 0.099562 & 1890.756482 \\ HER-02-002 & Right Actuation & 0.200361 & 1890.839838 & 0.500902 & 1890.997388 \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Frequency-domain features for EMG sensors—glass grip. Figure 20: Paper grip—exercise example. Figure 21: Flex peak amplitude—paper grip: (**a**) HER-01-001 right hand; (**b**) HER-01-001 left hand; (**c**) HER-02-001 right hand; (**d**) HER-02-001 left hand; (**e**) HER-02-002 right hand; (**f**) HER-02-002 left hand. Figure 22: HER-01-001—EMG and accelerometer data FFT spectra—paper grip: (**a**) right hand and (**b**) left hand. Finally, to explore the monotonic relationships between participants' subjective ratings and their biomechanical signals, we computed Spearman rank-order correlations across all six participants, the the results of which are presented in Figure 26 below. Figure 24: HER-02-002—EMG and accelerometer data FFT spectra—paper grip: (**a**) right hand and (**b**) left hand. Figure 23: HER-02-001—EMG and accelerometer data FFT spectra—paper grip: (**a**) right hand and (**b**) left hand. \begin{table}
\begin{tabular}{l l c c c c c} \hline \hline
**Participant** & **Condition** & \begin{tabular}{c} **LH EMG Dominant** \\ **Freq (Hz)** \\ \end{tabular} & \begin{tabular}{c} **LH EMG Total** \\ **Power (\(V^{2}\))** \\ \end{tabular} & \
\begin{tabular}{c} **RH EMG Dominant** \\ **Freq (Hz)** \\ \end{tabular} &
\begin{tabular}{c} **RH EMG Total** \\ **Power (\(V^{2}\))** \\ \end{tabular} \\ \hline HER-01-001 & Non-actuated & 0.099354 & 1830.000000 & 0.099354 & 1830.000000 \\ HER-01-001 & Left Actuation & 0.796495 & 1890.282550 & 0.199124 & 1854.152767 \\ HER-01-001 & Right Actuation & 0.299880 & 1830.000000 & 0.099960 & 1830.000000 \\ HER-02-001 & Non-actuated & 0.200361 & 1886.492856 & 0.400721 & 1889.190431 \\ HER-02-001 & Left Actuation & 0.099562 & 1887.675208 & 0.298686 & 1883.218107 \\ HER-02-001 & Right Actuation & 0.701262 & 1890.172429 & 0.500902 & 1888.627353 \\ HER-02-002 & Non-actuated & 0.398248 & 1890.866749 & 0.099562 & 1890.583968 \\ HER-02-002 & Left Actuation & 0.400721 & 1890.911656 & 0.100180 & 1823.081392 \\ HER-02-002 & Right Actuation & 0.300541 & 1886.715516 & 0.200361 & 1890.946518 \\ \hline \hline \end{tabular}
\end{table} 
Table 16: Frequency-domain features for EMG sensors—paper grip.