The intake of sodium bicarbonate has no effect on end power and work above end power using the 3-min all-out test

Abstract

Introduction & Purpose
Sodium bicarbonate (NaHCO₃) is widely used to enhance buffering capacity during high-intensity exercise. However, the negative effects of acidosis, as well as the influence of NaHCO₃, remain questionable and controversial. This study aimed to investigate the effect of NaHCO₃ supplementation on performance parameters derived from a 3-min all-out cycling test (3MAOT).

Methods
Twelve well-trained male triathletes (age: 27±5.6 years, V̇O₂_peak:  60±8 mL∙min^-1∙kg^-1) volunteered for this double-blinded placebo-controlled study. Subjects were required to visit the laboratory at four occasions: (1) to determine their individual peak [HCO₃^-] following the ingestion of 0.3 g/kg body mass NaHCO₃; (2) to determine V̇O₂_peak, maximal aerobic power (MAP) and power output associated with the first ventilatory threshold using a graded exercise test and to familiarise with the 3MAOT (Burnley et al., 2006; Vanhatalo et al., 2007); (3) and (4) to perform the 3MAOT under both experimental conditions (NaHCO₃ and microcrystalline cellulose/isomaltulose placebo) in a randomised and alternating order to determine work above end power (WEP) and end power (EP). Respiratory gases were measured to analyse V̇O₂_peak and V̇O₂-on-kinetics, and blood lactate samples were collected prior and after the 3MAOT. Blood gas analysis was performed to assess pH and [HCO₃^-] using capillary blood samples. Nutrition, fluid intake, and capsule ingestion were standardised with individually timed ingestion (125±24 min prior) (AIS, 2025). Gastrointestinal symptoms were assessed using a questionnaire. Trials were separated by >48h. Paired-samples t-tests were used to compare WEP and EP variables between conditions. A two-way repeated-measures ANOVA was used to evaluate blood parameters. Effect sizes were calculated using Cohen’s d and .

Results

All data were normally distributed. No significant differences were found for WEP (p=0.513, d=0.20) and EP (p=0.789, d=0.08) as shown in Figure 1. Significant time x condition interactions for [HCO₃^-], pH, and maximal [lactate] following NaHCO₃ ingestion (all at p<0.001; <0.01<<0.80) were found. The analysis of V̇O₂-on-kinetics revealed non-significant differences for all parameters (i.e., mean response time, amplitude, oxygen-deficit) (all at p>0.050; <0.01<<0.59). No notable gastrointestinal symptoms were reported following NaHCO₃ ingestion.

Discussion
NaHCO₃ did not improve short-time all-out performance at group level in athletes. However, large interindividual variation suggests the presence of responders and non-responders to NaHCO₃. The increase in [lactate] in response to NaHCO₃ingestion may indicate increased glycolytic contribution or altered clearance kinetics, but this potentially enhanced glycolytic activity did not result in a significant performance improvement. NaHCO₃ did not alter V̇O₂-on-kinetics, suggesting no effect on temporal changes of oxidative metabolism at exercise onset.

Conclusion
Based on the present results, the intake strategy of 0.3 g/kg of NaHCO₃ can be considered a practical and well-tolerated strategy based on gastrointestinal symptom assessment. From a practical perspective, it appears most appropriate to assess the effects of NaHCO₃ on an individual basis due to the observed interindividual variation in performance changes. Similarly, the results suggest that a general recommendation for improving short time endurance performance using NaHCO₃ cannot be made even though physiological parameters such as pH, [HCO₃^-] or [lactate] indicate increased buffer capacity.

References

AIS. (2025) Sodium Bicarbonate Group A (AIS Sports Supplement Framework). Australian Institute of Sport. Retrieved 18.05. from https://www.ausport.gov.au/ais/nutrition/supplements/group_a/performance-supplements2/bicarbonate

Burnley, M., Doust, J. H., & Vanhatalo, A. (2006). A 3-min all-out test to determine peak oxygen uptake and the maximal steady state. Medicine and Science in Sports and Exercise, 38(11), 1995-2003. https://doi.org/10.1249/01.mss.0000232024.06114.a6

Vanhatalo, A., Doust, J. H., & Burnley, M. (2007). Determination of critical power using a 3-min all-out cycling test. Medicine and Science in Sports and Exercise, 39(3), 548-555. https://doi.org/10.1249/mss.0b013e31802dd3e6