## 4 Discussion  
Research indicates that velocity-based training can effectively improve various fitness attributes in athletes. However, there is a scarcity of studies focused on its effectiveness in soccer. Thus, this investigation aimed to compare the impacts of two in-season velocity loss methods (VL15 and VL30) with traditional strength training (TRT) on leg strength, change of direction ability, jumping, and sprinting performance in elite youth soccer players. The present study results confirmed that all the groups significantly increased their strength level, with no significant differences in strength-enhancing capacity between the groups. VL15 was proved to be superior to both VL30 and TRT in developing the reactive strength index (RSI) and COD test. In addition, all three groups significantly increased in their countermovement jump pre vs. post (\(p\) < 0.05), only VL15 significantly improved in RSI, and both VL 15 and VL30 significantly improved in their COD performance. In accordance with the initial hypothesis, it seems that adding two sessions a week for four weeks of velocity-based training with a relative load of 60-80% and velocity loss threshold of 15% appears to be a more robust strategy than VL30 or traditional strength training for lower body strength, jumping, and change of direction performance enhancement during the competitive period in elite youth soccer players. Ultimately, neither training method was shown to be effective in improving 20 m sprinting. A growing body of studies have recently emerged evaluating the impacts of different %VLs on the set on performance outcomes in athletic populations, with the presented \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**VL15**} & \multicolumn{2}{c}{**VL30**} & \multicolumn{2}{c}{**TRT**} & \\ \hline  & **IN** & **FIN** & **\%** & **d** & **IN** & **FIN** & **\%** & **d** & **IN** & **FIN** & **\%** & **d** & \(p\) \\ \hline SQIRM & 106.83 \(\pm\) 12.23 & \(\frac{115.83}{\pm}\) 12.50 & 8.4 & 0.72 & \(\frac{111.45}{\pm}\) 9.07 & 10.2 & 1.09 & \(\frac{105.00}{\pm}\) 7.51 & \(\frac{116.45}{\pm}\) 7.64 & 10.9 & **1.49** & 0.000 \\ CMJ & 56.63 \(\pm\) 7.94 & \(\frac{60.04}{\pm}\) 8.28 & 6.0 & 0.42 & \(\frac{50.51}{\pm}\) 4.72 & 53.65 \(\pm\) 4.97 & 6.2 & 0.66 & 50.98 \(\pm\) 4.77 & \(\frac{51.85}{\pm}\) 4.71 * & 1.7 & **0.18** & **0.000 \(\downarrow\)** \\ RSI & 2.45 \(\pm\) 0.21 & 2.75 \(\pm\) 0.26 * & 12.24 & 1.42 & \(\frac{1}{2.18}{\pm}\) 0.23 & 2.25 \(\pm\) 0.29 & 3.2 & 0.26 & \(\frac{2.27}{\pm}\) 0.33 & \(\frac{2.28}{\pm}\) 0.29 & 0.4 & **0.03** & **0.001 \(\uparrow\)** \\ SPR20m & 3.00 \(\pm\) 0.76 & 2.95 \(\pm\) 0.89 * & 1.6 & 0.06 & 3.07 \(\pm\) 0.43 & 3.02 \(\pm\) 0.33 * & 1.6 & 0.11 & 3.09 \(\pm\) 0.50 & 3.05 \(\pm\) 0.44 * & 1.2 & 0.08 & 0.587 \\ COD & 2.20 \(\pm\) 0.09 & 2.10 \(\pm\) 0.06 * & 2.4 & 1.11 & 2.27 \(\pm\) 0.10 & 2.22 \(\pm\) 0.10 * & 1.5 & 0.50 & 2.29 \(\pm\) 0.09 & 2.24 \(\pm\) 0.11 & 0.6 & 0.55 & **0.038 \(\uparrow\)** \\ \hline \hline \end{tabular}  
* statistically significant difference pre vs. post \(p\) < 0.05; \(\uparrow\)—statistically significant difference between VL15 and VL30 group; \(\downarrow\)—statistically significant difference between VL15 and TRT group.  
\end{table} 
Table 3: Pre–post and between-group differences between selected variables with % improvement and [PERSON]’s effect size (d). data generally in line with this study's findings. In an 8-week study involving 16 training sessions conducted by [PERSON] et al. [15], it was found that velocity-based training (VBT) with a 20% velocity loss produced squat strength gains similar to those achieved with a 40% velocity loss (18% and 13.4%, respectively). Additionally, the 20% velocity loss group demonstrated significantly greater improvements in counter-movement jump (CMJ) performance, showing an increase of 9.5% compared to just 3.5% in the 40% velocity loss group (\(p<0.05\)) among resistance-trained young athletes. The outcomes of the 8 weeks of [PERSON] et al.