# Single Camera-Based Remote Physical Therapy: Verification on a Large Video Dataset
## 3 Results  
In our study, we analyzed a total of 2133 videos. Each video shows only one trainee performing a unique exercise. Each video belonged to one of the \"Camera View\" and one of the \"Starting position\" groups. We present the results of our findings using OpenPose reported confidence values. We can use the confidence returned by the OpenPose algorithm as a measure of detection quality because it correlates with the percentage of correct keypoints metric [35]. The resulting median confidences for each joint and each category are shown in Table 4. Keypoints with a confidence value above 0.5 can be considered correctly detected [35]. These confidence values are associated with with clearly visible body parts [9]. Due to the large amount of data in the groups, the differences in confidence between groups are largely significant, although small in absolute terms. Therefore, for clarity, only differences that were not statistically significant (n.s.) are highlighted in the following boxplots. All the other differences were statistically significant, see Tables A1 and A2 in the Appendix A. Box-and-whisker plots of detection confidence for all the categories are show in Figures 4-9. When interpreting the plots, it is important to note that the confidence correlates nonlinearly with the detection accuracy. If all keypoints in the image are clearly visible and accurately detected, confidence values in the range of 0.7-0.9 are commonly obtained. From a practical perspective of a single camera-based recording, the differences in accuracy associated with this range of confidences are not relevant. Even points with a confidence value above 0.5 can be considered correctly detected [9]. Lower confidence values are also associated with high-frequency keypoint jitter [36], but this effect can be easily filtered out because the body movements during rehabilitation exercises are slow relative to the sampling rate of the camera. False-positive detections or swapped keypoints can only be expected for low confidence values around 0.2 [34]. Small confidence values (0.1) are associated with guessed and occluded keypoints; the smaller the value, the more false positives detections are likely [9]. \begin{table}
\begin{tabular}{l l c c c c c c c c c c c c} \hline \multicolumn{13}{l}{**Medians of Confidence for Selected Group and OP Keypoint**} \\ \hline \hline Camera View & \multicolumn{3}{c}{Front view} & \multicolumn{3}{c}{34 view} & \multicolumn{3}{c}{Side view} & \\ \hline Starting position & Ly & Kn & Si & St & Ly & Kn & Si & St & Ly & Kn & Si & St \\ \hline \multicolumn{13}{l}{No.} & KP name & & & & & & & & & & & & \\ \hline \multicolumn{13}{l}{Upper body} \\ \hline
2 & RShoulder & 0.67 & 0.65 & 0.78 & 0.80 & 0.62 & 0.67 & 0.77 & 0.79 & 0.68 & 0.68 & 0.76 & 0.78 \\ \hline
3 & RElbow & 0.75 & 0.81 & 0.82 & 0.84 & 0.76 & 0.81 & 0.82 & 0.84 & 0.78 & 0.82 & 0.81 & 0.83 \\ \hline
4 & RWrist & 0.75 & 0.79 & 0.82 & 0.84 & 0.75 & 0.80 & 0.82 & 0.83 & 0.79 & 0.81 & 0.81 & 0.83 \\ \hline
5 & LShoulder & 0.54 & 0.60 & 0.79 & 0.80 & 0.53 & 0.63 & 0.80 & 0.80 & 0.52 & 0.54 & 0.77 & 0.78 \\ \hline
6 & Lelbow & 0.39 & 0.78 & 0.81 & 0.83 & 0.66 & 0.78 & 0.79 & 0.81 & 0.41 & 0.72 & 0.79 & 0.79 \\ \hline \multicolumn{13}{l}{Lower body} \\ \hline
9 & RFlip & 0.42 & 0.48 & 0.64 & 0.64 & 0.38 & 0.51 & 0.66 & 0.64 & 0.40 & 0.49 & 0.59 & 0.64 \\ \hline
10 & RKnee & 0.62 & 0.75 & 0.80 & 0.79 & 0.61 & 0.78 & 0.81 & 0.78 & 0.65 & 0.78 & 0.78 & 0.78 \\ \hline
11 & Rankle & 0.54 & 0.64 & 0.73 & 0.79 & 0.53 & 0.68 & 0.71 & 0.79 & 0.56 & 0.67 & 0.69 & 0.78 \\ \hline
12 & LHip & 0.38 & 0.44 & 0.65 & 0.65 & 0.35 & 0.47 & 0.66 & 0.65 & 0.35 & 0.40 & 0.58 & 0.63 \\ \hline
13 & LKnee & 0.50 & 0.72 & 0.80 & 0.79 & 0.41 & 0.71 & 0.81 & 0.79 & 0.51 & 0.66 & 0.79 & 0.78 \\ \hline
14 & LAnkle & 0.43 & 0.54 & 0.71 & 0.78 & 0.40 & 0.65 & 0.71 & 0.78 & 0.47 & 0.55 & 0.68 & 0.78 \\ \hline \end{tabular}
\end{table} 
Table 4: Median confidence value for each specific group. Figure 4: Confidence of detection of selected KP (keypoints)—front view, upper body.