Bigfoot, and the mystery of lactic acid...

Bigfoot, and the mystery of lactic acid…

Bigfoot isn’t real. Well, at least I don’t think it’s real. I mean science tells me it’s extremely unlikely, but according to the stories I’ve been told as a kid, and the two hours per week that my dad watches “Finding Bigfoot” it is possible, I guess? So why do we as a culture accept that there is a real possibility that something with no scientific backing may exist… because someone at some point told us that’s the way it was (usually as children), and our uneducated common sense/our imagination wanted it to be real. Unfortunately, when you bring it up in your place of work as an educated adult, you may get some funny looks. Oh man is this going to be a bad take if they ever find one of those things…

Lactic acid, like Bigfoot to society, is one of the most commonly used misnomers in exercise science. There is some truth, as we do know that lactate has an impact on high intensity exercise, but what impact it does have is commonly mistaken. I would imagine reading this, most of you have heard the term “lactic acid buildup” or “clearing lactic acid” used regarding what causes muscle fatigue, burning, or soreness during and after high intensity exercise. I’m here to tell you that you’ve been misled; the people using the terms aren’t wrong in the sense that lactic acidosis and lactate are involved in the process, but they are completely wrong on the impact they have on your muscles. The scary part is it’s become a part of exercise science culture, type it in Google and you’ll come away with multiple “scientific” or “health” websites that lead you to believe lactate acid is the cause of all your problems. To better understand what really occurs, we need to understand a few concepts first…

What’s ATP, lactate, and pyruvate? Why do they matter?

The small molecule ATP, which stands for adenosine triphosphate, is the main energy carrier for all living things. In humans, ATP is a biochemical way to store and use energy for every single cell in the body. ATP energy is also the primary energy source for other animals and plants. The way ATP works is that your body takes food products (carbs), breaks them down, and turns them into fuel for the body. The breakdown process can happen with or without oxygen. But ATP is used a bit quicker in the absence of oxygen (anaerobic). (1)

According to Janet Hamilton, a registered clinical exercise physiologist and run coach at Running Strong in Atlanta, lactate—which is a byproduct of stored carbohydrates—is there for a reason.

Hamilton explains that when you break down carbohydrates to make ATP (energy), your body also creates something called pyruvate. In most instances, pyruvate goes onto the next stage of metabolism, known as the krebs cycle, to create more ATP. This is a process that requires oxygen (aerobic). It usually happens when you’re carrying out regular daily activities like walking to the grocery store, for example. When you work out at a high intensity, however, your need for ATP increases, so your body produces ATP anaerobically (i.e. without oxygen), because it’s a faster process with fewer steps. (4)

That got a little science-y, but the main concept to understand is your body takes longer to create energy using oxygen, so when you’re attempting a max lift, or sprinting 100 meters, the body compensates and uses ATP as its main energy source. (1) It’s also important to understand that your body does not create lactic acid through intense exercise, it creates lactate.

The myth that is “lactic acid”

So, we’ve already determined that lactic acid isn’t created during high intensity exercise, lactate is. Most athletes believe that lactate causes muscle fatigue by making the muscles too acidic (or changing the Ph levels) to contract effectively. That’s not the case, while the muscles do become more acidic during exercise, it is due to the hydrogen ion that lactate carries with it, not the lactate itself. (5) In any case, lactate accumulation in the muscles delay fatigue by lessening the effects of a phenomenon known as depolarization. Depolarization in short, is when your muscles run out of calcium ions to create muscle contraction. During intense exercise, your muscles lose power in the same way a battery does: by becoming depolarized. The accumulation of lactate in muscle tissue during intense exercise partly counteracts the effect of depolarization. Contrary to popular belief, lactate doesn’t “build-up” in certain areas of your body because your body efficiently redistributes it elsewhere. If there’s enough lactate in an area, then the body naturally recognizes that, and it will shuttle the lactate either to another cell nearby. Or it will send it off to the heart, where it can be utilized as fuel. (3)

“Lactic acid build up makes you sore”

It doesn’t... The simplest proof of this is the fact that very little lactate is produced during highly prolonged, low-intensity exercise (aerobic), and yet it is this very type of exercise that leaves the muscles sorest in the following days. Think about how sore you are (or would be) after a marathon or a half-marathon, it’s not physiologically possible for lactate to be the culprit for that soreness. Muscle soreness is generally caused by muscle damage, inflammation, and free radical damage. (4) Which creates adaptions in the body as it heals, ultimately leading to our improved fitness!

“Better athletes train to produce less lactic acid”

False, are you starting to catch my drift here J? You would only think this if you assumed lactate production slows the contraction of muscles, which we’ve previously discussed that it does the opposite. What very well may be occurring in extremely high-level athletes is they’re able to use more of their lactate to increase muscle production. For example, if we assume 80% of lactate is used on the muscles, and 20% escapes into the bloodstream, then elite athletes may be able to use 90% of the lactate in their muscles, only losing 10% into the bloodstream. (3) That’s more of theory than scientific fact just yet, but the important part to grasp is elite athletes are not producing less lactate, it wouldn’t be advantageous for them to do so. With that theory their muscles would fatigue faster, not slower.

So, is there any truth to it?

Most of the newer developments in understanding the impact of lactate on high intensity exercise is due to new technology in the field. Studies started coming out in the mid to late 90’s questioning the idea that lactic acid and pH imbalances were the common cause for muscle fatigue. Most of the studies that were done in defense of the theory were “correlation” type studies, meaning they didn’t know that Elvis killed Bigfoot, they just knew that Elvis and Bigfoot were in the same room and Elvis had the knife. Now with the advancement in being able to test muscles in humans directly, scientists can get a much better perspective of lactate during exercise… turns out it wasn’t Elvis.

How does it actually happen then?

Long story short, your muscle needs calcium ions to contract, when it runs low on calcium through physiological pathways the firing rate and force output of your muscles slow down. At the same time lactate is trying to prevent your muscles from running out of calcium ions, so it’s trying to keep the muscles firing at a high rate. The increased lactate production creates higher muscle contractions, which create higher levels of muscle damage aka soreness. The burning sensation you get is from the blood accumulation in the area, and at extremely high levels of acute continuous exercise the hydrogen ions can change Ph levels in the blood. Most commonly you see this in sled pushes or true max effort force outputs (50 calories on the assault bike). The dramatic change in pH can cause nausea and overall body weakness, yet it has little to nothing to do with acute muscle fatigue. In most cases the burning goes away soon after the exercise stops, because the blood leaves the area and the body redistributes the lactate (and hydrogen) along with it.

As in anything, this is still a hotly debated subject with some smart people on both sides of the fence. A lot like the Bigfoot situation… I guess? Either way, the emerging science has shown a plethora of evidence to support the idea that lactic acid is an oversimplified myth, and that lactate is our friend, not our foe. I hope you have a much better understanding of how our muscles work, I think you’ll be surprised how many people overuse the term “lactic acid” in the following weeks and months. You can be the bearer of bad news and let them know once and for all, Bigfoot isn’t real J .

Sources:

1. Cairns SP. Lactic acid and exercise performance – culprit or friend? Sports Med. 2006;36:279–291.

2. Brooks GA. Lactate doesn't necessarily cause fatigue: why are we surprised? J Physiol. 2001;536:1.

3. Fitzgerald, M. (2014, January 24). Six Lies You Were Taught About Lactic Acid. Retrieved from Competitor Running: https://running.pocketoutdoormedia.com/six-lies-you-were-taught-about-lactic-acid_29432

4. Hensley, L. (n.d.). What is Lactic Acid and Does it Really Cause Muscle Soreness? Retrieved from Aaptive.com: https://aaptiv.com/magazine/lactic-acid

5. Robergs, Robert A.; Ghiasvand, Farzenah; Parker Daryl (2004). "Biochemistry of exercise-induced metabolic acidosis". American Journal of Physiology. Regulatory, Integrative and Comparative Physiology. 287 (3): R502–16.