Monitoring seasonal changes in jump ability and shoulder strength in young volleyball players across age and competitive levels

This study aims to investigate differences in jump performance and upper-limb strength among youth female volleyball players, analyzing the influence of category (U14, U16, U18), competition level (regional vs. local), and time point within the season (pre- vs. mid-season). Sixty-four athletes were evaluated using countermovement jump (CMJ), drop jump (DJ), and maximal voluntary isometric contraction (MVIC) tests for shoulder internal and external rotation. Performance metrics were analyzed via three-way MANOVAs. Results revealed significant effects of session, category, and level on jump performance, with U18 and regional-level players consistently outperforming their peers. All groups improved from pre- to mid-season, reflecting training adaptations and natural growth. However, the interaction effect was not significant, suggesting that all groups improved similarly regardless of category or level of competition. Shoulder strength assessments showed improvements throughout the season, but no consistent differences were observed based on level. The findings suggest that while older and higher-level athletes demonstrate superior baseline performance, seasonal improvements are relatively uniform, likely influenced by maturation processes. This study highlights the value of jump and strength analyses in youth volleyball over a season, providing practical guidance for coaches to tailor training programs and track physical development in adolescent athletes. In addition, the inclusion of percentile values represents a valuable resource for coaches, offering benchmarks to estimate expected performance by category and to better interpret individual improvement across the season.