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Old June 20th, 2013 (8:58 AM).
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Kanzler Kanzler is offline
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Join Date: Jul 2008
Location: Toronto
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Does cardio really lead to muscle loss? My biochem instincts have always been writhing whenever I hear that. Your body doesn't start stripping away muscle until you're effectively starving, like sub-1500 calories, but even only then for an extended period of time. I find don't find it very believable that muscle turns into fuel when you have perfectly adequate fat cells that store, well, energy. Most cells can undergo the beta-oxidation process that gets the fat molecule inside the mitochondria of that same cell. But for proteins, and if you're talking about stripping away muscle fibres, well that to me sounds like proteolysis. And after you've broken down the protein to amino acids, you have to get rid of the amino group, which sounds like a trip to the liver. The whole process sounds terribly inefficient, especially the second part about the muscle cell (or almost every other cell type in the body) being unable to convert the protein into what can actually be used as energy (fat or sugar). I feel that cardio can only lead to muscle loss when you're doing seriously long distance running, burning thousands of calories that you don't immediately replenish because you're running for so long. Which is probably something none of us are doing, so we're pretty safe from that fate.