Lactic Acid Myths

From Matt Fitzgerald

The February 2009 issue of Triathlete Magazine contains a feature article, which I wrote, entitled, “The Lactic Acid Myths.” It summarizes the latest scientific knowledge of lactate metabolism, which includes the following points: 1) the human body does not produce lactic acid at all, but lactate; 2) lactate does not cause muscular acidosis; 3) muscular acidosis is only a minor cause of muscle fatigue; 4) muscle cell depolarization is a much more potent cause of muscle fatigue during high-intensity exercise; 5) lactate actually delays fatigue caused by muscle cell depolarization; 6) the body can recycle lactate to glucose, the muscles’ primary source of fuel for high-intensity exercise; 7) lactate can be directly oxidized inside cellular mitochondria to yield energy (in other words, far from being a byproduct of anaerobic metabolism, lactate is an aerobic fuel); 75 percent of the lactate produced by the muscles during exercise never leaves the muscle cells but is used directly for energy; 9) lactate production during exercise upregulates genes that generate new mitochondria (in other words, high levels of exposure to lactate during exercise lead to physiological adaptations that strengthen aerobic capacity).