Lactic Acid: Myth or Misunderstood?


We’ve all heard of lactic acid building up in our muscles during exercise, but there are new findings calling this common knowledge into question. In the past, scientists found that after exercise our muscles are more acidic (which reduces their ability to contract) and contain a substance - lactate - that wasn’t there before. Putting the two together, it was assumed that in producing energy using anaerobic energy systems, lactate was formed as a byproduct which caused our muscles to become more acidic - this was referred to as lactic acidosis. As it was found that a similar substance (lactic acid) was present in animal tissues, the terms lactate, lactic acidosis and lactic acid all became interchangeable and were used to explain the same thing, despite being slightly different from each other. Lactic acid was the most popular and catchy term, which is why it gained widespread use and is the most familiar to us.

Today, thanks to scientific advances, we know a lot more about how acids and ions work. This prompted a review of exercise metabolites, and it was found that lactate was formed as a result of acid in the muscles, instead of causing it. Lactate is used to reduce the acidity in muscles and can be broken down afterwards for more energy. If we keep moving after intense exercise (jogging, light movement) instead of coming to a complete stop, this encourages the body to process the lactate quicker to create more energy.

With this knowledge, we can utilise high intensity interval training (HIIT) with light recovery exercise between sets to force our bodies to process lactate faster, which train our bodies to reduce the acidity of our muscles quicker and help us recover faster. Examples of HIIT can be found in activities such as Crossfit, Grit classes and interval sprint training for sports.


Ever since the 19th century, it’s been common knowledge that continuous exercise produces a nasty chemical called lactic acid in our bodies, causing a burning sensation in our muscles and preventing them from contracting as forcefully. With enough lactic acid, our muscles reach failure and stop working all together.

Thanks to Roger Robergs and his team, it turns out we were wrong. Very wrong.

We don’t even produce lactic acid, strenuous exercise or not.

So where did we slip up? Let’s take a look.


Physiologists were studying muscle fatigue in frogs. Well not whole frogs, just their legs. By stimulating the muscles with electrical impulses, they could simulate the nerve sending them signals to contract. What they found was that after a period of contraction, the muscles would become fatigued and contract less forcefully. Analysing the muscle fibres afterwards, they found they had become acidic, which limited the muscles ability to contract (as certain chemical reactions weren’t able to take place in an acidic environment). They also found concentrations of lactate, which wasn’t there at the start of the experiment.

From this, they concluded that muscle fatigue was due to the build up of an acidic environment, caused by the acidic lactate or acidic lactate salts, and so named this condition lactic acidosis. People swap around the terms lactate (or acidic lactate salts) to lactic acid, because while they are all substances that are milky in appearance and occur in animal tissue, lactic acid is catchier to say. Also, because the proper term was lactic acidosis instead of “lactate acidosis”, lactic acid is what first entered people’s minds when thinking/talking about it.

This idea of lactic acidosis - and from that, lactic acid in muscles - made sense. So it stuck.


By now, science has come a long way in terms of technique and equipment to analyse the chemical reactions of the body, and had discovered that there were more systems at work in our muscles that could provide energy for movement without the use of any oxygen molecules (anaerobic reactions - these guys will pop up again later), and they would be used for quick bursts of intense exercise or when oxygen wasn’t available for prolonged bouts of intense exercise. Most notably the work of Otto Meyerhoff and Archibald V. Hill; who were awarded Nobel prizes for their work in uncovering the role of carbohydrates for energy production in skeletal muscle during exercise.

With the understanding of biochemistry of the time, they inferred that it was plausible that one of the end products of these anaerobic reactions could be lactic acid, and demonstrated the chemical equations necessary to make this a reality. At this time there were also numerous papers and experiments demonstrating the existence of lactic acid in animal tissues and fermentation processes, adding value to the idea that cells were producing lactic acid (or acidic lactate salts, making the cell environment acidic). Combining these factors, it was generally accepted that there was indeed lactic acid, or acidic lactate salts, produced as a result of these anaerobic chemical reactions to produce energy.

 Unfortunately, while it does all look nice and neat, this is still a bit off.


While studying exercise metabolites (what molecules are produced as a result of the chemical reactions taking place during exercise), Roger Robergs and his collegues found that things didn’t quite add up. With a greater understanding of biochemistry thank to modern advances, they were able to apply new knowledge about how molecules interacted with each other, in particular acids and what the mitochondria in our cells get up to with specific ions, and what they found kinda tipped all the previous conclusions on their head.

In short, what they found was that instead of lactate causing any lactic acidosis, lactate is produced as a RESULT of this acid build up; and far from hindering our performance, lactate actually ENHANCES it.

Hmm. Didn’t see that coming.


The following section is a brief summary of all the biochemical science involved (to include everything would make this article hella-lengthy), but the original and fully detailed article by Robergs et al. can be found clicking here or via the link down in the “Sources/Further Reading” section at the end of this article. In short, acid is created as a byproduct in the muscles during intense exercise, but we also produce lactate that binds to the acid and transports it out of the muscles to keep them working hard, and then gets recycled into more energy.

Feel free to skip the biochemistry bit below and move onto the next section to find out how to use it to your advantage in training.

It’s fine. Skip it. It only took me a billion hours to write.

Brief Biochemistry

The body primarily burns through energy using oxygen in chemical reactions (aerobic reactions), and while this produces a lot of energy, it is also a slow process. With intense exercise, there comes a tipping point where we need more energy than our bodies can provide oxygen for. At this point, we rely more on chemical reactions that don’t need oxygen (anaerobic reactions), which use different molecules to produce energy. They don’t produce quite as much energy as the reactions with oxygen, but we can’t be fussy. We need the energy to survive the next round of intense exercise.

In these anaerobic reactions, some extra molecules are produced (pyruvate and hydrogen ions - also known as protons) along with the energy to allow the muscle to continue contracting. The pyruvate molecules can be broken down further to produce more energy, and the protons start to build up in our cells.

These protons can be shuttled away from the cell, but it takes a little time. By continuing to exercise, these protons will continue to build up faster than they can be taken away, and they will start to lower the pH of the cell, making it more acidic. This is what the burning sensation is in our muscles. An acidic environment also makes it harder for chemical reactions to take place, so our muscle fibres can’t contract as hard or as fast, which reduces our performance.

 This is where lactate comes in.

To combat the growing number of protons in the cell, pyruvate can consume 2 protons and BECOME lactate.

(That’s what previous scientists missed. They didn’t have the science we do today, and so did not know the pyruvate could absorb the protons (aka hydrogen ions) and become lactate. For them, it seemed as though lactate was the end product and dropped protons - making the environment acidic - to go on to become pyruvate).

From here, the newly formed lactate can travel to the liver to dispose of the protons, and become pyruvate again, which can be broken down and used for more energy. By using lactate to get rid of protons, this raises the pH of the cell (back towards normal levels) and we can contract our muscle fibres harder/faster than when they were full of protons. Also, the burning sensation diminishes - thank goodness.

This is what previous scientists had missed - lactate is CAUSED by the acid in our muscles, they simply got things the wrong way round. and is able to ENHANCE our performance, by keeping us moving beyond what we would be able to do without it (and becoming overcome by protons/”the burn”).


Traditionally, back when we thought we produced lactic acid or that lactate was a bad thing, trainers would implement Lactic Threshold training - or tempo runs for runners. The way to do this was to work hard enough to make your muscles utilise anaerobic reactions to make energy (to produce lactic acid as a by-product), and to keep on working through it. Rest, and repeat later. Everyone hates it.

The idea behind it is to build up a tolerance to “lactic acidosis”, so that we could train for longer before the acidosis kicked in and our performance diminished, and also to build resistance to it once it did.

This, of course, was before we knew lactate was good for us and help get rid of acidosis.

By shifting our perception from “tolerating” lactate, to optimising its intended use (transporting acid out of the muscles, and aiding recovery by being broken down into pyruvate for energy), we can train in a way that let’s us benefit from better acidosis buffering and recovery, as our body processes the lactate more efficiently. The key phrase here is “process the lactate”.

Before, we would enter into a bout of intense exercise and then allow our bodies to take it’s time to recover - long rest so there’s no rush. Now we know this is pushing our bodies the wrong way - emphasising high levels of acidosis instead of the recovery from it.

By focusing on our recovery (using lactate and the reactions involved more efficiently) we can process the protons in our muscles quicker, and break down the lactate quicker to be used for extra energy, allowing us to exercise for longer. So instead of a long period of high intensity with a long rest, we should still utilise a long period of high intensity, but with a much shorter rest.

This will kick the lactate processing reactions into gear, forcing them to work harder to get rid of the acidosis and convert the lactate into energy quicker. Everyone hates this too, but at least now we’re getting more results from it.

Let’s take a look at some real world training applications.


The simplest way to implement this kind of training is using intervals: work hard for a set time, have a short active rest (don’t stop moving, just slow down) and hit another hard set, repeating this for at least 3 cycles. By having a short active rest, this forces our bodies to work harder to clear the lactate and acid out of our muscle cells in preparation for the next bout of intense exercise, making it adapt to training by recovering quicker.

How intense the exercise is (fast-as-possible-sprints or simply a fast pace) is up to you, but what matters is that you’re working hard enough to “feel the burn” of acidosis. To progress each week; either maintain the same pace for a longer period of time (keeping the short rest period the same), or increase the intensity for the same period of time (by adding weight or moving faster), and keep the short rest period the same length of time.

This is the basis of high intensity interval training (HIIT), and we can see examples of it in workouts that are used in Crossfit, Insanity, Grit and Pump exercise classes. While they are also great for weight loss, the intense exercise with short rest periods provides a great way to improve your lactate processing reactions, and so improve your recovery and allow you to continue working hard for longer (as you’re able to process protons out of your muscle cells more efficiently, so you can keep your muscles working for longer).

These classes can be a great way to get started and get in the HIIT mindset for improving your general fitness, but you can also apply it to sport specific movements. For example, sprints for swimming or hill climbs for runners and cyclists; same idea just go hard, have a quick rest, then get back on it.


Thanks to continued research, we now know something we once thought to be a damaging waste product, is in fact part of a key energy system that helps us to perform better and for longer. We can incorporate this into our training by utilising a form of HIIT (high intensity interval training) - strenuous exercise with a short rest, rinse and repeat - which will help develop our lactate processing and allow us to recover quicker from bouts of strenuous exercise.

Crazy to think such a commonplace idea was flawed all this time, interesting though. Shows that we’re always learning, always able to look at things from different perspectives and get some new insights.

I’d love to know your thoughts on the matter, and any questions or feedback you have. Just write it down in the comment section or drop me a message via social media or using one of the contact forms on the site.

All the best and keep crushing it,



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Robergs RA. 2011. Counterpoint: Muscle lactate and H+ production do not have a 1:1 association in skeletal muscle. Journal of Applied Physiology. May. 110(5). Pp 1489-1491

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