Abstract / Summary
Objective To evaluate the relative effects of dietary supplements, the certainty of evidence, and the robustness of findings within separate networks for peak power (PP), relative peak power (RPP), vertical jump (VJ), and countermovement jump (CMJ).Methods PubMed, Web of Science, Embase, and the Cochrane Library were systematically searched, with the final search conducted on September 8, 2026. Eligible studies were randomised parallel-group and crossover controlled trials published in English through August 31, 2026, involving healthy individuals with physical activity or training backgrounds. Four separate Bayesian random-effects networks were constructed. Effects were assessed using mean differences (MDs) in change scores, 95% credible intervals (CrIs), and prediction intervals. Risk of bias and certainty of evidence were assessed using RoB 2 and CINeMA, respectively. Subgroup analyses, network meta-regression, and sensitivity analyses were also conducted. This review was retrospectively registered in PROSPERO (CRD420261283835).Results A total of 119 studies were included. The PP, RPP, VJ, and CMJ networks comprised 47, 33, 31, and 44 studies, respectively, with some studies contributing to more than one outcome. Compared with placebo, β-hydroxy-β-methylbutyrate (HMB) yielded MDs of 64.70 W (95% CrI: 19.15 to 110.50) for PP and 0.84 W·kg−1 (95% CrI: 0.42 to 1.28) for RPP. Favourable effects were also observed for β-alanine on PP and for creatine and vitamin D on RPP. Iron supplementation yielded an MD of 6.81 cm (95% CrI: 0.84 to 12.83) for VJ, supported by only one direct study. For CMJ, betaine yielded an MD of 3.72 cm (95% CrI: 1.24 to 6.18); the 95% CrIs for palmitoylethanolamide, caffeine combined with Rhodiola rosea, creatine, multi-ingredient supplements, and caffeine also excluded zero. The HMB findings for RPP remained relatively stable across multiple sensitivity analyses, whereas some other favourable comparisons had prediction intervals that included zero or showed attenuated findings in sensitivity analyses. Exploratory associations with training level and sport were observed for RPP, although interpretation was limited by sparse evidence and imbalanced covariate distributions. Of 1,636 pairwise comparisons, 17 were rated as moderate, 55 as low, and 1,564 as very low certainty. The HMB-versus-placebo comparisons for both PP and RPP were rated as moderate certainty.Conclusions Some supplements showed favourable effects within their respective networks, with the HMB findings for RPP remaining relatively stable. However, direct evidence was limited, and the certainty of evidence was very low for most comparisons. Findings should be interpreted in the context of the populations and supplementation regimens studied. Differences between networks cannot establish that outcome type modifies supplementation effects, and rankings alone should not be used to guide individualised supplementation regimens.