Effects of nutritional supplementation on physical performance and sport-specific skills in volleyball players: a systematic review and meta-analysis

Background: Nutritional supplementation is widely used to support sports performance; however, evidence specific to volleyball players remains fragmented. This systematic review and meta-analysis aimed to evaluate the effects of nutritional supplementation on physical performance and sport-specific skills in competitive volleyball players. Methods: Following PRISMA guidelines, five electronic databases were systematically searched. Randomized controlled trials investigating acute or chronic nutritional supplementation in healthy volleyball players were included. Outcomes included vertical jump performance, muscle strength, agility, and sport-specific technical skills. Risk of bias was assessed using the Cochrane tool, and random-effects meta-analyses were performed. Results: Thirteen randomized controlled trials involving 240 participants were included. Nutritional supplementation was associated with significant improvements in vertical jump performance (SMD = 0.47, 95% CI: 0.24-0.70), muscle strength (SMD = 0.43, 95% CI: 0.17-0.69), agility (SMD = 0.89, 95% CI: 0.54-1.24), and sport-specific technical skills (SMD = 0.63, 95% CI: 0.31-0.95). Subgroup analyses indicated beneficial effects following both acute and chronic supplementation protocols, with minimal statistical heterogeneity across outcomes. Conclusion: Within the available evidence, nutritional supplementation may contribute to improvements in selected physical performance and sport-specific skill outcomes in competitive volleyball players. These findings may inform evidence-based nutritional strategies aimed at supporting sports performance in volleyball, while highlighting the need for larger, ecologically valid trials.