Effects of Sodium Bicarbonate Supplementation on Muscular Strength and Endurance: A Systematic Review and Meta-analysis.

BACKGROUND The effects of sodium bicarbonate on muscular strength and muscular endurance are commonly acknowledged as unclear due to the contrasting evidence on the topic. OBJECTIVE To conduct a systematic review and meta-analysis of studies exploring the acute effects of sodium bicarbonate supplementation on muscular strength and endurance. METHODS A search for studies was performed using five databases. Meta-analyses of standardized mean differences (SMDs) were performed using a random-effects model to determine the effects of sodium bicarbonate supplementation on muscular strength (assessed by changes in peak force [N], peak torque [N m], or maximum load lifted [kg]) and muscular endurance (assessed by changes in the number of repetitions performed, isokinetic total work, or time to maintain isometric force production). Subgroup meta-analyses were conducted for the muscular endurance of small vs. large muscle groups and muscular strength tested in a rested vs. fatigued state. A random-effects meta-regression analysis was used to explore possible trends in the effects of: (a) timing of sodium bicarbonate ingestion; and (b) acute increase in blood bicarbonate concentration (from baseline to pre-exercise), on muscular endurance and muscular strength. RESULTS Thirteen studies explored the effects of sodium bicarbonate on muscular endurance and 11 on muscular strength. Sodium bicarbonate supplementation was found to be ergogenic for muscular endurance (SMD = 0.37; 95% confidence interval [CI]: 0.15, 0.59; p = 0.001). The performance-enhancing effects of sodium bicarbonate were significant for both small (SMD = 0.31; 95% CI: 0.04, 0.59; p = 0.025) and large muscle groups (SMD = 0.40; 95% CI: 0.13, 0.66; p = 0.003). Sodium bicarbonate ingestion was not found to enhance muscular strength (SMD = - 0.03; 95% CI: - 0.18, 0.12; p = 0.725). No significant effects were found regardless of whether the testing was carried out in a rested (SMD = 0.02; 95% CI: - 0.09, 0.13; p = 0.694) or fatigued (SMD = - 0.16; 95% CI: - 0.59, 0.28; p = 0.483) state. No significant linear trends in the effects of timing of sodium bicarbonate ingestion or acute increase in blood bicarbonate concentrations on muscular endurance or muscular strength were found. CONCLUSIONS Overall, sodium bicarbonate supplementation acutely improves muscular endurance of small and large muscle groups, but no significant ergogenic effect on muscular strength was found.