Oral sodium bicarbonate increases extracellular bicarbonate concentration, which facilitates the efflux of hydrogen ions from muscle cells and reduces intracellular acidosis.

Study: Sodium bicarbonate for kidney transplant recipients with metabolic acidosis in Switzerland: a multicentre, randomised, single-blind, placebo-controlled, phase 3 trial.

Taking sodium bicarbonate pills did raise the bicarbonate level in the blood, which is exactly what the claim says it does. This means it likely helps remove acid from muscle cells, even though the study didn't measure muscles directly.

Study: Effect of Oral and Topical Sodium Bicarbonate on Functional Recovery and Soccer-Specific Performance After Exercise-Induced Muscle Damage: A Randomized, Double-Blind, Placebo-Controlled Study

Taking baking soda by mouth didn't make muscles feel less sore, but it helped soccer players run and change direction better after intense exercise — likely because it helped their muscles get rid of acid buildup.

Study: The effect of sodium bicarbonate mini-tablets in a carbohydrate hydrogel on prolonged high-intensity cycling performance and metabolism in acute normobaric hypoxia

Taking baking soda by mouth raised the level of bicarbonate in the blood, which helps pull acid out of muscles, making it easier to exercise harder and longer — and the study proved it worked.

Study: A Comparison of Sodium Citrate and Sodium Bicarbonate's Safety and Effectiveness in Treating Metabolic Acidosis in Patients with Chronic Renal Disease

Taking sodium bicarbonate by mouth raised bicarbonate levels in the blood, which helps remove excess acid from the body — just like the claim says. Even though they didn’t measure muscle cells directly, this is how the body normally reduces acid buildup.