## 4 Discussion
[101] described significant increases in CMJ and peak power in volleyball players after eight weeks of Thera-Band training; however, applying these findings beyond volleyball presents limitations in generalizing results to handball. Similarly, [PERSON] et al. 's [106] findings, focused on bodyweight and pylometric protocols without resistance bands, while relevant for their economical and functional approach, do not directly attribute benefits to this specific training modality. In contrast, the results of this meta-analysis offer a substantially more robust and specific body of evidence. In particular, the eight comparisons on resistance band training in formative-stage handball players showed statistically significant and consistent improvements in vertical jump performance, both in CMJ (SMD = 1.69; 95% CI: 1.11 to 2.27) and SJ (SMD = 1.46; 95% CI: 1.06 to 1.85), with low to moderate heterogeneity levels (global I\({}^{2}\) = 14%). This sustained and homogeneous effect reinforces the relevance of this intervention modality not only as a practical solution but also as an effective and scientifically validated strategy to enhance neuromuscular performance in young handball players. This underscores the need for the systematic incorporation of such interventions into physical training programs for developmental stages, especially in contexts with limited access to specialized equipment. Despite the reported benefits, methodological limitations persist, affecting the strength of the results. A significant proportion of the studies included in this review exhibited deficiencies in essential experimental design aspects, such as the lack of participant and assessor blinding, allocation concealment, and absence of pre-established protocols. These omissions increase the risk of bias, particularly in performance and detection domains, as revealed by the Cochrane Risk of Bias Tool. Additionally, critical variables such as biological maturation or pubertal stage were not systematically considered, and most studies did not disaggregate results by gender, limiting the interpretation of subgroup-specific differences. This methodological gap hinders a precise understanding of training responses during sensitive developmental stages. This scenario contrasts with sports like football and rugby, where studies such as [PERSON] et al. and [PERSON] et al. have more rigorously integrated biological maturity control and standardized training load criteria [26; 31]. These approaches have proven effective in reducing variability in training effects and enhancing practical transferability. Similarly, [PERSON] and [PERSON] [24] emphasized the need to tailor interventions to the athlete's developmental stage, highlighting the urgency of adopting these criteria in youth handball. Furthermore, heterogeneity in protocol planning (volume, frequency, duration, and intensity) poses another challenge. While partly reflecting the principle of individualized training, there is a pressing need for greater systematization to enable valid comparisons between studies and facilitate the practical application of the evidence. From a developmental perspective, the findings of this review and meta-analysis clearly reinforce the necessity of designing physical training programs that align with the comprehensive developmental needs of children and adolescents. Rather than applying homogeneous approaches or replicating adult-oriented models, current evidence supports that interventions during formative stages must align closely with biological timing, motor development trajectories, and psychosocial conditions of young athletes. Models such as Long-Term Athlete Development (LTAD) emphasize that chronological age alone is insufficient as an organizing criterion for training, advocating for consideration of variables like biological maturity, sociocultural environment, and specific learning needs [24; 105]. However, the studies analyzed in this review demonstrate the irregular implementation of these principles.