Dietary Supplement Strategies During Conditioning Training in Athletes: A Network Meta-Analysis of Peak and Mean Anaerobic Power, VO2max, and Endurance Performance.

Dietary supplements are often used during training to support energy provision, recovery, and adaptation, yet effects on peak and mean anaerobic power, VO2max, and endurance performance remain inconsistent. Unlike prior syntheses centred on neuromuscular outcomes (strength and hypertrophy), this study compared six common supplements-protein, creatine, β-alanine, HMB, vitamin D, and nitrate-on energy-system performance (peak anaerobic power, mean anaerobic power, VO2max, and endurance performance) using network meta-analysis. PubMed, Web of Science, Cochrane Library, Embase, and SPORTDiscus were searched from inception to 15 March 2025 for RCTs examining dietary supplements and athletic performance. Risk of bias was assessed with the revised Cochrane tool. Random-effects network meta-analyses were conducted in R 4.3.1 and Stata 18. Thirty RCTs involving 693 athletes undergoing training programmes combined with supplements or placebo met the inclusion criteria. For peak anaerobic power, protein (SMD 0.85; 95% CI 0.27-1.44; SUCRA 82.9%; moderate certainty), creatine (0.62; 0.20-1.03; 62.5%; moderate), HMB (0.60; 0.28-0.94; 60.7%; moderate), and β-alanine (0.58; 0.09-1.07; 57.4%; very low) were superior to placebo. In mean power, β-alanine (0.75; 0.20-1.31; 74.1%; very low), protein (0.74; 0.27-1.20; 73.9%; very low), and creatine (0.74; 0.08-1.39; 71.0%; very low) showed consistent benefits, while HMB provided a moderate improvement (0.45; 0.05-0.86; 45.8%; very low). Endurance performance improved only with protein (0.99; 0.16-1.83; 94.3%; very low). No supplement affected VO2max. Protein most effectively enhances peak power and endurance performance; β-alanine and creatine excel in mean power; creatine and HMB also aid peak power; none improve VO2max. Trial Registration: PROSPERO identifier: CRD420251106522.