Lactate is not responsible for muscle fatigue, the burning sensation, or muscle soreness; on the contrary, it plays a beneficial role in various physiological processes.

noli's read

The idea that lactate (or lactic acid) accumulation causes muscle acidosis is a physiological myth widely refuted by modern science. Research, notably studies published in the Journal of Physiology, shows that lactate is actually a valuable energy fuel for the muscles and the heart, and that it even helps buffer intracellular acidity rather than causing it. The burning sensation is more closely linked to the accumulation of hydrogen ions resulting from ATP hydrolysis, a distinct process. As for muscle soreness (DOMS), current scientific consensus (via systematic reviews on recovery) indicates that it results from muscle micro-tears and associated inflammation, not from the presence of lactate, which is eliminated very rapidly after exercise. The claim is therefore extremely solid and consistent with current knowledge in exercise physiology. There is no exaggeration here, but rather a necessary correction of a persistent popular belief.

the sources

No named source held this one up — that absence is part of the verdict.