## 4 Discussion
Despite similar strength gains (22.3%, ES = 1.39 vs. 19.4, ES = 3.09), velocity-based training was proved to produce more favorable improvements in CMJ (7.3%, ES = 0.53), RSI (23.9%, ES = 0.85) and the COD test (4.6%, ES = 0.87). In addition, no group-by-time interaction and no significant improvements were found for sprint performance, altogether corroborating the present study's findings. Interestingly, only a few studies have compared the effects of VBT with different %VL and/or traditional resistance training on performance within a population of soccer players [21; 22; 23]. Two previous studies, [PERSON] et al. (2017) and [PERSON] et al. (2024), compared resistance training programs in male soccer players using similar %VL in the set (10 vs. 30% and 15% vs. 30%, respectively). Although the range of relative loads used was lower (50-70% 1 RM and 45-60% 1 RM), the results obtained were generally in line with the present study's findings: groups the lower velocity loss in both studies showed larger improvements in countermovement jump (5.3%; ES: 0.40 and 8.0%, ES: 0.51) and similar in 1 RM strength (5.3%; ES: 0.45 and 22.2, ES: 1.65). In addition, while sprint time showed no significant improvements pre vs. post in the [PERSON] study (0.4%: ES 0.10), being practically identical to the present study's findings, [PERSON]'s study reported significant and large sprint time pre vs. post improvements (11.3%, ES: 1.85). This difference could likely be attributed to both the younger age of this study's participants compared to both ours and [PERSON]'s study, as well as the resistance training history (resistance training naive cohort). Finally, to the best of our knowledge, only one study compared the effects of velocity-based training and traditional strength training. [PERSON] et al. [23] examined the effects of VBT (20% velocity drop threshold with load equivalent to 65% of 1 RM) vs. TRT (load equivalent to 80% of 1 RM) on 30 sprint time, countermovement jump, lower body maximum strength, and maximal squat power. The presented data indicate that the VBT group, with a 42% lower volume of training, produced significant increases in maximal strength (_p_ < 0.000), squat power (_p_ < 0.000), 30m sprint time (_p_ < 0.000), and countermovement jump (p\(<\) 0.001), with squat power and CMJ being meaningfully better than the results of the TRT group (_p_ < 0.008). Together, the aforementioned data support the effectiveness of velocity-based training in enhancing strength and power performance attributes in well-trained youth soccer players. However, it is essential to exercise caution regarding the threshold load required to achieve the desired improvements. Clearly, further research on this topic is needed. It is noteworthy that we did not find significant effects of either velocity-based training or traditional resistance training on the 20 m sprint time among our participants. This aligns with the findings of [PERSON] et al. (2017), who reported no change in 20 m sprint times following lower load velocity-based training in professional soccer players. It can be speculated that the obtained results may be partly due to the training status of the current study's participants (well-trained), as research has shown that trained adolescents tend to improve less in sprint outcomes with resistance training than their untrained peers [32]. Furthermore, the training and testing specificity may influence outcomes, as the upward force vector applied during this study training sessions is likely crucial for inducing specific functional adaptations [33]. The present study results demonstrated significant changes in the performance parameters when utilizing velocity loss methods, with smaller velocity losses usually eliciting greater neuromuscular adaptations compared to larger velocity losses. Although this study does not address them, it is worth briefly hypothesizing the mechanisms that could explain the observed improvements in the performance outcomes.