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FeepingCreature comments on Dark Arts of Rationality - Less Wrong
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Huh? What are you talking about? Placebo does work (somewhat, in some cases). Placebo even works when you know it's a placebo. Even if you don't use these techniques. There's studies and everything.
The brain is absurdly easy to fool when parts of it are complicit. Tell yourself "I will do twenty push-ups and then stop", put your everything in the twenty knowing you'll stop after, and after you reach twenty just keep going for a few more until your arms burn. This will work reliably and repeatably. Your brain simply does not notice that you're systematically lying to it.
He did call it a trap. (And I have a feeling that that's something that has happened to me quite often, though I can't think of any good particular example I'd be willing to share.)
Isn't the feeling of pain when you exercise too much There For A Reason?
(OK, it might be there for a reason that applied in the environment of evolutionary adaptedness but no longer applies today. But as a general heuristic I'm wary of refusing to listen at what my body is telling me unless I'm reasonably sure what I'm doing.)
The model I'm familiar with is that muscular soreness comes from microscopic trauma to the muscle fibers being exercised, and that the same trauma ultimately leads to increased strength (as muscles adapt to prevent it). That's clearly a simplified model, though: for example, later exercise can help ease soreness (though it hurts more to start with), while the opposite would be true if it was a pure function of trauma.
With my sketchy evopsych hat on, I might speculate that it helps prevent possible damage from overexertion, but that people in the EEA would rapidly habituate to their normal (albeit very high by our standards) levels of activity. Now that we're relatively very sedentary, such a signal, at least at its ancestral levels of sensitivity, might end up being counterproductive from a health perspective.
From the “reliably”, “repeatedly” and “systematically” in FeepingCreature's comment, I guessed they weren't talking about a previously sedentary person just starting to exercise. (I think I was going to clarify I was mainly talking about the middle and long term, but forgot to.) I do expect it to be normal for my muscles to hurt when I've just started exercising after weeks of inactivity.
The "feeling of pain when you exercise" is just lactic acid.
Essentially, your body has multiple pathways to generate energy. The "normal" one uses oxygen, but when you spend energy too fast and your lungs and blood cannot supply and transport enough, the cells switch to another pathway. It's less efficient but it doesn't need oxygen. Unfortunately a byproduct of this metabolic pathway is lactic acid and it is precisely its accumulation that you feel as the muscle "burn" during exercise.
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