## 2 Materials and Methods
### Procedures
#### 2.2.1. Maturity Status  
Beyond the consideration of chronological age, we evaluated the stage of biological development of each participant. Biological age was assessed specifically using the biological age proportional method [25]. An anthropometric measurement was performed on each participant, based on which the body structure development index (KEI) was calculated. The anthropometric measurement was carried out in accordance with ISAK (International Society for the Advancement of Kinnthropometry) international standards [26]. Stature (cm) was measured using the Tanita HR-001 anthropometer (Tanita, Tokyo, Japan) with a measurement error of 5 mm. Body weight (kg) was measured using the InBody 770 device (Biospace, Seoul, Republic of Korea). The accuracy of measurement when determining body weight was 100 g. To determine the representation of monitored body composition fractions (kg; %), a non-invasive method of multi-frequency tetrapolar bioelectrical impedance (BIA) was employed using the InBody 770 device. BIA devices of this type show the highest degree of validity and reliability of measurement [27]. During the BIA examination, the emphasis was on compliance with the conditions and measurement procedure recommendations [28]. The medical tape measure (Holtain, Crymych, UK) was used to determine the circumferential characteristics. The circumference of the arm (right) in flexion (cm) and the maximum circumference of the calf (right, cm) were evaluated. The width and bone \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Early Maturation** & **Average Maturation** & **Late Maturation** \\ \cline{2-4}  & **\(n\) = 17** & **\(n\) = 46** & **\(n\) = 35** \\ \cline{2-4}  & **M \(\pm\) SD** & **M \(\pm\) SD** & **M \(\pm\) SD** \\ \hline
**Age (years)** & 12.95 \(\pm\) 0.26 & 13.21 \(\pm\) 1.37 & 12.93 \(\pm\) 0.50 \\
**Stature (cm)** & 168.58 \(\pm\) 6.38 **\#** & 161.36 \(\pm\) 10.18 \({}^{\text{ }}\) & 151.99 \(\pm\) 6.11 \\
**Body mass (kg)** & 54.92 \(\pm\) 5.96 **\#** & 49.16 \(\pm\) 9.38 \({}^{\text{ }}\) & 39.30 \(\pm\) 4.23 \\
**Fat mass (\%)** & 11.47 \(\pm\) 4.43 & 11.64 \(\pm\) 4.11 & 11.15 \(\pm\) 4.63 \\
**FFM (kg)** & 48.59\(\pm\) 5.67 **\#** & 43.45 \(\pm\) 8.80 \({}^{\text{ }}\) & 34.86 \(\pm\) 3.77 \\
**SMM (kg)** & 26.92 \(\pm\) 3.41 **\#** & 23.90 \(\pm\) 5.37 \({}^{\text{ }}\) & 18.73 \(\pm\) 2.25 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Basic characteristics of groups according to maturation status. diameters were determined with a touch gauge with extendable arms--Pelvimeter P-216 (Trystom, Olomouc, Czech Republic). The biepicondylar width of the lower epiphysis of the humerus (cm) and the biepicondylar width of the lower epiphysis of the femur (cm) were evaluated. The Best II K-501 caliper (Trystom, Olomouc, Czech Republic) with a contact surface of 3 mm and a pressure force of 2 N was applied to assess the values of subcutaneous body fat (skin folds). Skin folds (mm) on the right half of the body were assessed above the crest of the hip bone (suprailica), the skin fold on the arm (above the triceps brachii muscle halfway between the acromiale and radiale points), the skin fold on the back (below the lower angle of the scapula) and the calf II skin fold (in the medial part at the point of highest development of m. triceps surea). Body constitution expressed by somatotype was assessed using the Heath-Carter methodology [29]. The research data were processed using appropriate procedures in the Antropo program version 2000.1. [30]. Further data processing took place in the specialized Testbal program [31]. Data backup for all conducted research investigations was carried out anonymously and in accordance with the applicable GDPR provisions. The backup was stored in a data cloud managed within the scientific and technical park of the institution [32]. Subsequently, player groups of different biological ages were created.