Effects of Nutritional Supplements on Explosive Lower Limb Performance in Volleyball Players: A Systematic Review and Network Meta-Analysis.

β-alanine was associated with the greatest improvement in vertical jump height among volleyball athletes.

• β-alanine showed a mean difference of 4.6 cm (95% CrI 1.2–7.8) for vertical jump height
• This was the largest effect size among the 13 different supplements examined
• The finding was based on a Bayesian network meta-analysis of 35 RCTs (n = 838 volleyball athletes)
• Certainty of evidence was appraised as low-to-moderate using CINeMA

Creatine and caffeine were also effective for improving vertical jump height in volleyball athletes.

• Creatine showed a mean difference of 3.7 cm (95% CrI 0.57–6.9) for vertical jump height
• Caffeine showed a mean difference of 2.1 cm (95% CrI 0.06–4.1) for vertical jump height
• Both creatine and caffeine had statistically significant credible intervals that did not include zero
• 13 different supplements in total were examined across the included trials

β-alanine was the most promising supplement for increasing lower limb peak power in volleyball athletes.

• β-alanine was associated with an SMD of 1.1 (95% CrI 0.21–2.0) for lower limb peak power
• The standardized mean difference indicates a large effect size
• SUCRA ranking placed β-alanine as the top-ranked supplement for this outcome
• The credible interval did not include zero, indicating statistical significance

No statistically significant improvement in lower limb mean power was found for any supplement examined.

• Despite significant effects on peak power and vertical jump, mean power outcomes did not reach statistical significance for any supplement
• This finding was consistent across the 13 supplements examined
• No serious adverse events were reported across any of the supplement interventions

The systematic review included 35 RCTs examining 13 different nutritional supplements in volleyball athletes.

• Total sample size was 838 volleyball athletes across all included trials
• Eligible participants were volleyball athletes aged ≥14 years
• Interventions required a minimum duration of ≥1 week
• Databases searched included PubMed, Web of Science, CENTRAL, and Embase from inception to 1 August 2025
• A Bayesian network meta-analysis was used to estimate effects with 95% credible intervals and SUCRA rankings

The certainty of evidence for supplement effects on explosive lower limb performance in volleyball was rated as low-to-moderate.

• Certainty was appraised using CINeMA (Confidence in Network Meta-Analysis)
• Authors concluded findings 'should be interpreted with caution and regarded as preliminary'
• Authors called for 'high-quality, standardized randomized controlled trials' to validate findings
• Supplement strategies were recommended to be individualized by age and competitive level