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Nornagest comments on Dark Arts of Rationality - Less Wrong
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Comments (185)
This appears to have been discredited.
(Note however that DOMS is only one component of the muscle soreness following exercise; but lactic acid doesn't seem to have been implicated in the others either, at least as far as five minutes of Google can tell me. ATP and H+ ions may be involved in the acute version.)
I'm not talking about delayed onset, I'm talking about pain when you exercise (not after).
Recall the original statement that you were answering: "Isn't the feeling of pain when you exercise too much There For A Reason?"
I'm finding that somewhat harder to research (it doesn't seem to have received as much medical attention, possibly because it's such a short-term effect), but the papers I have turned up are equivocal at best. It might be one of several metabolites involved; it doesn't seem likely to be the sole culprit.
Well, I am sure there are other factors as well but I haven't seen it disputed that lactic acid is a major contributor to the "burning" feeling during the exercise. Wikipedia goes into biochemical details.
I agree that lactic acid is much less relevant to post-exercise pain and soreness.
The 'lactic acid causes burning' idea is mostly just hearsay. There is no evidence to support it, and a lot of evidence that lactic acid actually helps buffer the pH and keep acidosis from occurring: http://www.ncbi.nlm.nih.gov/pubmed/15308499
This seems controversial, see e.g. http://ajpregu.physiology.org/content/289/3/R902
P.S. Thanks for the link. That was an entertaining paper to read with authors going on "No, stop saying this, dumbasses, it doesn't work like that" rants every few paragraphs :-) I am now willing to agree that saying "lactic acid causes acidosis" is technically incorrect. In practice, however, it remains the case that glycolysis leads to both acidosis and increase in the lactic acid concentration so there doesn't seem to be a need to change anything in how people train and exercise.
That article you linked is a personal letter to the editor of that journal, and as such is not an indicator of controversy. The authors of the original study defended their viewpoints: http://ajpregu.physiology.org/content/289/3/R904
Obviously there was some debate but the defenders of lactic-acid acidosis never actually published results refuting that study, and indeed other studies that came after it all supported the hypothesis that lactic acid buildup does not contribute to muscle fatigue. For instance, this study carried out by freshmen, of all people: http://www.ncbi.nlm.nih.gov/pubmed/19948679
Interesting. The question, though, isn't whether the lactic acid causes muscle fatigue but whether it causes the characteristic "burning" sensation in the muscles.
Seems like I need to read up on this...
The term 'fatigue' seems to be inconsistently used to sometimes refer to DOMS and sometimes to the, as you call it, 'burning' sensation in the muscles. However, in both studies I linked, it's being used to refer to the fatigue during and immediately after exercise, not DOMS.