Abstract
BACKGROUND: Sodium bicarbonate (SB) supplementation may enhance short-term, high-intensity exercise performance through improved extracellular buffering capacity, but its effect on continuous running performance has not been systematically evaluated. We conducted a systematic review with meta-analysis of randomized, double-blind, placebo-controlled trials examining the effects of oral single-dose SB supplementation on continuous running performance. METHODS: We searched Medline, Embase, and the Cochrane Central Register of Controlled Trials for eligible trials published through 31 December 2024. The primary outcome was performance on a continuous running test. Secondary outcomes included gastrointestinal (GI) symptoms and GI-associated study withdrawal rates. Running performance was analyzed using random-effects meta-analysis with adjustment for GI-related study withdrawals using intent-to-treat methods and publication bias using the trim-and-fill method. Treatment effects were reported using the standardized mean difference (SMD) statistic where 0.00-0.19 represents negligible benefit, 0.20-0.49 small benefit, 0.50-0.79 medium benefit, and ≥ 0.80 large benefit. We used univariable meta-regression to examine factors associated with treatment effect magnitude. The certainty of evidence was assessed using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach. RESULTS: Among 11 studies with 126 participants, all used a cross-over design. Most (84%) subjects were male, SB dose was typically 0.3 g/kg, and performance test durations ranged from 1 to 30 minutes (median: 4 minutes). GI symptoms occurred more frequently with SB than placebo (29.5% vs. 2.6%; odds ratio = 5.9; p = 0.003; low certainty), as did GI-related study withdrawal (8.7% vs. 1.6%; odds ratio = 2.9; p = 0.049; moderate certainty). After adjusting for GI-related study withdrawal and publication bias, the treatment effect of SB was negligible and not statistically significant (SMD = 0.18; 95% CI: -0.01, 0.36; p = 0.06; I(2) = 0%; moderate certainty). In meta-regression, male sex (p = 0.03) and higher body mass (p = 0.04) were associated with greater SB performance benefits. In the 8 studies that enrolled males only, the treatment effect of SB was small and statistically significant (SMD = 0.40; 95% CI: 0.18, 0.63; p < 0.001). CONCLUSIONS: SB supplementation has a negligible benefit on continuous running performance in a mixed-sex population, the ergogenic effect may be more pronounced in males, GI symptoms are common, and some users may not tolerate supplementation. Athletes should carefully weigh the potential performance benefit of SB against the risk of GI symptoms and establish individual tolerance during training before considering use during competition.