<![CDATA[Vertical jump performance is essential in volleyball, supporting successful spiking, blocking, and jump serving. Despite extensive research on plyometric exercise, limited evidence exists regarding the effectiveness of structured jump box training for adolescent athletes in community volleyball clubs. This study evaluated the impact of an eight-week jump box training program on vertical jump performance. A quantitative pre-experimental design with a one-group pretest–posttest approach was employed. Twelve volleyball athletes aged 15–20 years from the Mutiara Muda Volleyball Club completed sixteen training sessions over eight weeks. Vertical jump height was measured before and after the intervention using the Vertical Jump Test. Data analysis included descriptive statistics, the Shapiro–Wilk normality test, and a paired-samples t-test at a 0.05 significance level. Average jump height improved from 46.50 cm at baseline to 57.42 cm after training. Normality assumptions were satisfied (pretest p = .612; posttest p = .500), while the paired-samples t-test demonstrated a significant increase in performance (t = −7.045, p < .001) with a very large effect size (Cohen's d = 2.034). These findings suggest that progressive jump box training effectively enhances lower-body explosive power and vertical jump ability in adolescent volleyball players.]]>
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