## 4 Discussion  
The main aim of this research was to observe whether there were differences, according to biological maturation, in the kinanthropometric characteristics and physical performance of young handball players. In this line, significant differences were found in basic measurements, muscle mass (MM), body mass index (BMI), Formic Index, medicine ball throw and SJ jump, with the group of early maturers having the highest values. Regarding the kinanthropometric characteristics, these results are similar to those found in previous studies performed both in handball players [10; 42; 43] and in other sports [26; 27; 44; 45]. In both cases, athletes with early biological maturation obtained higher values in kinanthropometric characteristics. These differences between the biological maturation groups may be due to the hormonal changes that occur during this stage [11]. In fact, it has been observed in previous research that the maturational process seems to have a statistically significant influence on kinanthropometric variables [13]. The pairwise  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{3}{*}{**Variable**} & \multirow{3}{*}{ \begin{tabular}{c} **Group** \\ **Comparison** \\ **SD** \\ \end{tabular}  } & \multicolumn{6}{c}{**BM\({}^{\prime}\)Age**} & \multicolumn{6}{c}{**BM\({}^{\prime}\)Maturity Offset**} & \multicolumn{6}{c}{**BM\({}^{\prime}\)KM**} \\ \cline{3-10}  & & \multicolumn{2}{c}{**Mean**} & \multicolumn{2}{c}{**Mean**} & \multicolumn{2}{c}{**Mean**} & \multicolumn{2}{c}{**Mean**} \\  & & **Difference \(\pm\)** & **\(p\)** & **95\% CI** & **Difference \(\pm\)** & **\(p\)** & **95\% CI** & **Difference \(\pm\)** & **\(p\)** & **95\% CI** \\  & & & & & & **SD** & & & & \\ \hline \multirow{3}{*}{MB} & E-A & 0.82 \(\pm\) 0.23 & 0.002 & 0.25 to 14.0 & 0.03 \(\pm\) 0.03 & 0.866 & \(-\)0.04 to 0.11 & 1.03 \  
comparison of the present investigation showed significant differences between the early maturer group with the average maturer group in body mass, height, sitting height, arm span and MM, also finding, apart from those mentioned, significant differences in BMI, BMI z-value and Cormic Index when comparing the early maturers with the late maturers. More specifically, in all these differences, early maturers had higher values. This could be due to an increased concentration of sex hormones or growth hormone (GH) around the APHV [11]. Moreover, on the one hand, the differences in body mass and MM could be due to these sex hormones, as they have an important role in the accumulation of muscle tissue [11; 14]. Additionally, on the other hand, the GH hormone influences height and sitting height, so it could also explain the higher values of early maturers in these variables [46]. Therefore, it seems that biological maturation influences kinanthropometric characteristics and that taking this variable into account could be a determining factor in the selection of future talents [10]. However, more research is still needed where the study population is handball players to contrast the results of the present investigation. Regarding sports performance in physical tests, it has been observed that the increase in MM influences an improvement in power production [47]. In fact, in this research, early maturers are the ones with higher MM and better values in the medicine-ball-throwing test and SJ jump, which are related to upper and lower limb power, respectively [4]. Furthermore, the pairwise comparison showed significant differences between the early maturer group and the rest of the groups for the medicine ball throw and with the average maturer group for the SJ jump. More specifically, the players who were more advanced in biological maturation showed better values. The reason for these differences may be due to muscle development due to hormonal changes in biological maturation [11], which implies higher values of MM in early maturers, as shown in our research, and, therefore, better values in tests related to strength and power [48].