Fig. 1

Schematic representation of the mechanism of HCO₃^- absorption in the stomach and the impact of sodium bicarbonate ingestion on muscle metabolism and selected blood parameters. Sodium bicarbonate ingestion increases the concentration of HCO₃^- in the stomach lumen, some of which neutralizes HCl to form CO₂ and increases luminal pH. The rise in pH stimulates the Cl^-/HCO₃^- antiporter in the parietal cells, which transports HCO₃^- into the extracellular fluid. This transport is coupled with the H-K-ATPase pump that secretes H⁺ into the stomach lumen to restore the pH. This results in increased pH and HCO₃^- concentration, which increases the activity of monocarboxylate transporters (MCT1 and MCT4, represented in light blue), thereby enhancing the transport of H⁺ out of muscle cells and improving intramuscular acid-base balance. Improved pH control in the muscle cells allows higher glycolytic rates, resulting in higher rates of ATP production and higher muscle and blood lactate concentrations. Solid lines indicate reactions. Dashed lines indicate transport across membranes or movement within the cell compartment. Created using BioRender.com