MythBusters: The Lactic Acid Edition 

Lactic Acid. The evil, but unavoidable waste product generated by your body during periods of intense activity. Man, if I had a rand for every time I heard “Flush the lactic acid out” or “My legs are still full of lactic acid” …well, I’d be writing this article from some exotic location in the Mediterranean instead of at my slightly less exotic desk in Johannesburg. But no one paid me for eavesdropping and the truth is that the lactic acid left your legs long ago. 

So, let’s clear up some of the myths around this natural metabolic by-product and see how lactic acid is not actually a bad thing, but is just misunderstood, like that weird kid in the corner nobody talks to. 

Myth #1 – Lactic acid stays in your body for a prolonged period & is the cause of pain when you feel the “burn”. 

Full disclosure, I, like so many other young trainers once believed this myth whole-heartedly and used to do silly things like 20 – 30 minutes low heart rate recovery time on the bike. But of course, you don’t recover from anything by doing more of it. 

In actual fact, lactic acid is naturally flushed out by the body minutes after of the end of your training session and within an hour will have returned to its baseline level. And, the fitter you are, the faster it’s recycled. Training methods like HIIT and sub-maximal training work wonders to improve the ability to recycle lactic acid even faster. (Note, I use the word recycle, not, flush out. More on that in Myth #2.) 

As for the “burn”, it’s not lactic acid that’s to blame for the burning sensation you feel during intense exercise, but increased acidity in the blood caused by the build-up and release of hydrogen ions. 

Myth #2 – Lactic acid is waste and causes muscle fatigue. 

During muscle contraction, stored glucose is broken down into lactic acid. The body then has the amazing ability constantly to produce and recycle lactic acid even when at rest. It’s estimated that roughly 75% of lactate produced inside the muscle cells is recycled into glucose and used as fuel for further exercise or movement. I don’t know about you, but that doesn’t sound like a total waste product to me.  In further support of this point, new research suggests that lactic acid not only helps to produce fuel but also acts as its own source of fuel for the body during intense periods of exercise.