PURPOSE: This study aimed to investigate the impact of a 6-week upper-body plyometric-training (PT) program with varying volumes on the immunoendocrine, physiological parameters, and physical performance adaptations in male volleyball players. METHODS: Twenty-four trained college players were randomly allocated into 3 groups with 8 participants. Each group performed 5 exercises at maximal effort with differences in volume: low (3 sets of 7 repetitions), moderate (3 sets of 10 repetitions), and high (3 sets of 13 repetitions). The training program lasted 6 weeks with participants undertaking 3 sessions of PT per week. RESULTS: Following the intervention, all groups exhibited significant (P = .001) improvements in physical and physiological parameters, as well as skill-based performances, with effect sizes ranging from small to very large. Comparative analysis of individual changes indicated that the high-volume group resulted in greater adaptive responses in the medicine-ball throw (P = .004), peak (P = .001) and average (P = .022) power output, push-ups (P = .001), and strength (P = .032) compared with the low-volume group. No significant between-groups difference (P >
.05) was observed regarding immunoendocrine measures, reaction time, attacking, and serving skills. CONCLUSIONS: The findings indicate that short-term upper-body PT positively influenced performance adaptations, emphasizing that the adaptive response to PT depends on the varying volumes. The study proposes that integrating higher volumes of PT results in more significant adaptive responses among volleyball players with the same immunoendocrine responses as the other training volumes.