# Analysis of Surface EMG Parameters in the Overhead Deep Squat Performance
## 2 Materials and Methods
### Studied Group Characteristic  
The %MVC, _MF_, _MDF_, _kurt_, and _CA1_ values were obtained as the results of analysis of the archival, raw sEMG signals. In this study, the sEMG signals recorded for 20 adult men were analyzed. The average age of the examined persons was 25.89 years (range: 23-29), and the average body mass index (BMI) was 24.78 kg/m\({}^{2}\) (range: 22.4-26.8). The study group consisted of representatives of various sports, including basketball players, volleyball players, and personal trainers. All participants train regularly as active sportsmen and have not suffered from previous injuries or contusions. According to the physiotherapists, the athletes selected for this study did not have over-trained muscles. During sEMG recordings, standard silver/chloride (Ag/AgCl) surface electrodes were used. The conductive surface of the electrode was about 38 mm\({}^{2}\). The electrodes were placed according to SENIAM (Surface Electromyography for the Non-Invasive Assessment of Muscles) recommendations [20]. Examples of actual electrode placement are shown in Figure 2. The sEMG signals were acquired with the VICON system, with the sampling frequency set at 1000 Hz, and processed in MATLAB (R2023a).  
In these studies, the correctness of the deep squat performance was assessed by physiotherapists on a point scale, which was based on 13 dichotomous variables with Yes/No (1/0) categories. Finally, the obtained sum of scores from the deep squat assessment was rescaled to a percentage scale from 0% to 100%. Physiotherapists evaluated the view of the front, side, and back, as well as the trunk, shoulders, and depth of squat, which is the usual procedure described in the literature [21; 22]. A detailed description of the criteria for physiotherapists assessment is presented in Table 1.  
According to the physiotherapists' assessment, three groups were distinguished in the analyzed data: group 1, with the evaluation of the correctness of deep squat ranging from 23% to 54%; group 2 (62-77%), and group 3 (85-92%). The higher the group index, the more accurately the deep squat was performed.  
Examples of orthogonal views of right, front, and top projection during deep squat for each examined group are shown in Figure 3. The presented drawings were created in MOKKA (Motion Kinematic & Kinetic Analyzer (ver. 0.6.2)) software based on the values of trajectory markers recorded during deep squat exercises with the VICON system.  
The number of subjects in the indicated groups was 5, 11, and 4, respectively, which means a total of 240 sEMG signals were analyzed (20 subjects \(\times\) 2 (left and right sides) \(\times\) 6 muscles).  
Figure 2: The electrode placement: (**a**) rectus femoris (top electrodes), vastus medialis (bottom electrodes), (**b**) biceps femoris, (**c**) deltoid, (**d**) latissimus dorsi.  
Figure 3: Examples of orthogonal views of right, front, and top projection during deep squat for each of the examined groups: (**a**) group 3, correctness level 85–92%; (**b**) group 2, correctness level 62–77%; and (**c**) group 1, correctness level 23–54%.