## 2 Materials and Methods
### Procedures
#### 2.4.2 Data Acquisition
After performing all the proposed exercises, the researcher showed each participant a video demonstration of the application, exposing all the functionalities and its layout. Then, the potential interest of the participants in using the smartphone app was questioned. To analyze the movement variation in Qualisys Motion Capture System, angles were calculated for each segment between two lines formed by anatomical markers. For the analysis of the head segment in both exercises, the markers left and right anterior head (L/RALH) and left and right acromion (L/RCAJ) were considered. Regarding the trunk segment, the markers left and right acromion (L/RCAJ) and left and right anterior superior supine (L/RIAS) were considered for both exercises. For the analysis of the shoulder segment, in the D1 exercise, the markers right acromion (RCAJ), right anterior superior supine (RIAS), and right lateral elbow (RELB) were used. In the M90 exercise, we contemplated the right acromion (RCAJ), right lateral elbow (RELB), and right distal ulna (RULN) markers for the analysis of the shoulder segment. Before and after calculating each angle, the \"fit to 2 nd degree curve\" filter was applied. For the smartphone app kinematic analysis, the recorded videos from guided exercises (GE) were directly compared to the non-guided exercises (NGE) for each participant. This analysis was performed (to all video frames) by calculating a similarity score between the landmarks from head, trunk, and shoulder segments of both videos. For the relevant landmarks, the distance between both videos was calculated using the cosine similarity. After comparing both videos, the average similarity was calculated, and if a predefined threshold was reached, that frame was considered similar. To calculate the final score representing movement quality, the similar number of frames was measured against the \begin{table}
\begin{tabular}{c c c} \hline \hline
**Exercise** & **Initial Position** & **Final Position** & **Description** \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Description of the diagonal shoulder exercise (D1) and multi-joint exercise, including shoulder external rotation at 90\({}^{\circ}\) of shoulder abduction (M90) used for the kinematic analysis. total, e.g., for a specific landmark, if we had an exercise video with 100 frames and 80 were deemed as similar, the final score would be 80%. For the optoelectronic systems data, the final score was determined based on a comparison of the range of movement of guided exercises (GE) and non-guided exercises (NGE), which represents the percentage of approximation of the range of motion (ROM) obtained for each segment. The percentage of approximation of the range of movement (ROM) obtained for each segment with the guided exercises against the non-guided exercises was designed as movement quality index and was assessed by using the following Formula (1):  
\[\textit{Movement quality index}\ (\%)=1-\ \frac{(\textit{ROM}_{GE}-\textit{ ROM}_{NGE})}{\textit{ROM}_{GE}}\times 100 \tag{1}\]  
After the collection and processing of the data provided by the instruments, they were exported to a Microsoft Excel for Microsoft 365 spreadsheet [33].