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2 things lactic acid does NOT do:

  1. Make you tired

  2. Make you sore

The lactic acid lie began with frogs. Yes, that’s right, frogs. In 1922, researcher Otto Fritz Meyerhof decided to remove a frog’s legs, place them in a jar and run electrical stimulation through them to make the muscles contract. Eventually the muscles stopped contracting (can you believe it?!) and when he examined them, he discovered that there was an enormous amount of lactic acid (lactate and hydrogen ions or acid) present. Huh? He concluded that the lack of oxygen (because the muscles were no longer attached and alive…what a shock!) resulted in the large amounts of lactic acid; and our falsely held belief in the lactic acid theory – that muscle fatigue is caused by lactic acid – was born! Travel down the timeline to 2015 and ask any regular exerciser, “What makes your muscles tired when you’re exercising? What makes you sore?” Most likely you’ll hear “lactic acid” as the response. Research has come a long way since 1922. In fact a lot of changes have occurred in the last decade or more. When my coaches at Malone used to do finger pricks to check lactic acid levels, they weren’t quite hitting the mark. We now know that lactic acid is NOT the reason for muscle fatigue or soreness. In fact, “lactic acid” is actually another fuel source for your muscles to use to continue to contract and keep you moving!

Here is the simple explanation. Your body has 3 methods of producing energy to keep you moving. The Glycolytic System (anaerobic exercise), which requires no use of oxygen to create energy, produces lactic acid or lactate and hydrogen ions. This type of exercise, which produces lactic acid, is short, quick bouts of intense activity. It also kicks in once your aerobic system has been maxed out. The byproducts of anaerobic exercise are lactate and hydrogen ions (or acid). However, the lactate and acid from anaerobic exercise doesn’t stick around for long in the body. Aerobic respiration works to clean up the lactate, using oxygen to burn it into carbon dioxide and water, which can be exhaled. The lactate can also be shuttled out of the muscles, into the blood, and burned in other areas of the body for more energy.

So, is there such a thing as “lactic acid production” during exercise? Not really. Your body certainly produces acid during exercise, and it produces lactate as well. But it’s the former, not the latter, that’s the main culprit for fatigue. Also, post-exercise muscle soreness (often thought to be a result of lactic acid still in the muscles) is actually caused by simple mechanical damage to muscle fibers, free radical damage, and inflammation, not lactic acid. Current research is showing that lactate is actually useful! It is metabolized aerobically in the mitochondria (energy producing factories in your cells) as a direct fuel for muscle contractions, so it is essentially doing the opposite of making you tired, its fueling future activity. Athletes who train at high levels of intense activity are likely to have lower levels of lactate, not because they produce less of it, but because their bodies learn to utilize it better. So, next time you’re “feeling the burn” or grunting as you get out of bed the day after a hard workout, don’t blame your fatigue and soreness on lactic acid…

it’s a lie!

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