Ingestion of sodium bicarbonate in a carbohydrate hydrogel increases the apparent strong ion difference (SID) during prolonged cycling in hypoxia, leading to altered extracellular electrolyte balance that enhances muscle excitability and reduces fatigue.

When sodium bicarbonate is swallowed with a carbohydrate gel, it enters the bloodstream and increases sodium and bicarbonate levels while lowering chloride and potassium levels outside muscle cells. This shifts the balance of charged particles to make the fluid around muscles more positively charged, which helps muscle cells maintain their ability to fire electrical signals and contract strongly, even when oxygen is low and acid builds up inside the cells.