## 2 Materials and Methods
### Data Processing  
The mean values of the CG (trajectory and velocity), hip joint (angle, velocity, and angular velocity), and shoulder joint (trajectory, velocity, and angular velocity) along the xy-axes during the execution of the CHCH were determined using kinematic methods in accordance with the standards of the Ariel Performance Analysis System (APAS). The APAS analyzes reference points across several phases. Female gymnasts were recorded during the competition using two SONY DVCAM DSR-300 PK digital cameras, positioned on the left and right sides of the apparatus at a right angle (90\({}^{\circ}\)) relative to the axis, which was perpendicular to the direction of the gymnasts' movement and passed through the middle of the apparatus (between the lower and higher bar) and the point of grip--the axis of rotation. The camera frequency was set to 50 Hz, as performed by [24; 25], while the resolution was 720 \(\times\) 576 pixels. The cameras were synchronized using an internal synchronous system. It was necessary to bring the participants' different starting positions to the same level, i.e., the same initial position, so that the APAS program could process the moderate space. The desired moderate space was adjusted so that all movements would be used as a reference against the first gymnast, representing absolute space. [PERSON] from Austria was used as the baseline for absolute zero in terms of height and length, and all other performances on the uneven bars were aligned within her reference space. In the starting position, the contestants should be facing the same direction so that the statistics (angle, speed, acceleration, angular velocity) can be recorded in the same coordinate system. The camera angles were selected based on the expertise of the Institute of Sports, Faculty of Sports, University of Ljubljana. The chosen recording angles revealed errors in plotting the coordinates along the \"x\" and \"y\" axes, as well as minor displacements along the \"z\" axis, although all exercises were successfully performed. Prior to recording, and for the purpose of accurate calibration of the measurement space, three reference frames--cubes (2 \(\times\) 1 m\({}^{3}\))--were positioned and leveled on the abutments of the uneven bars. Two cubes were placed one above the other in front of and behind the lower bar (Figure 2b), while the third was positioned in front of the higher bar (Figure 2c). Figure 2: Space moderation under the angle of 90\({}^{\circ}\) (**a**); of the low bar (**b**); and of the high bar (**c**). The conversion of video footage into quantitative data and the calculation of kinematic parameters for this research were conducted in accordance with the standards of the APAS. The APAS comprises two functionally interconnected units: a video camera (for signal collection) and a digitizer connected to a computer (for data acquisition). The criterion variable used to standardize all derived CHCHs was the exercise performed by [PERSON] (AUT) at the 39 th World Cup, which served as the baseline for absolute zero height and length for all other CHCH performances on the uneven bars. The different starting positions of the competitors were standardized to the same initial position, allowing the APAS to process the data consistently. It was necessary to align the different starting positions of the participants to a common level, or the same initial position, for the APAS program to process the movement area effectively. The reference area was adjusted to mirror the first gymnast's performance, which served as the baseline. All subsequent performances on the uneven bars were aligned to fit within this baseline. Each routine was rotated and adjusted so that the center corresponded with the axis of rotation. Calculated kinematic parameters were further prepared for statistical analysis. [PERSON]'s correlation was used to measure the strength and direction of the linear relationship between the performance variables of different gymnasts.