Lactic Acid- Debunking a common held fitness myth

Another day and another long held “Bro Science” theory to squash. This started during my morning workout when I forgot my headphones- FAIL. Now I hate not having music while I workout for a few reasons. First, it opens the door for people to come “converse” with you during your rest periods and my workouts are not social hour. Next it means I am stuck to listen to these mainstream trainers standing by their clients moving the pin up and down on the leg extension machine while spewing their “knowledge”. It takes everything I have to not butt in and save these people from the completely bogus information being disseminated to them.

(Thinking back, maybe I should be thanking these individuals- they always give me great writing prompts…)

This morning it was “How’s that lactic acid from our Monday workout treating you?”. That was my first palm to face. Then it was- make sure you do cardio tomorrow to get all that acid out of your muscles. That’s where I almost lost it.

Science people, science.

(Let me throw out there that the Personal Training industry is HIGHLY unregulated. You can get
certifications on Groupon for gosh sakes. You have to go to beauty school to cut hair, massage school to give massages, but can take a 30 minute online exam and call yourself a “Trainer”… really? Or take no exam and simply call yourself a “Health Coach” then tell people what supplements they should take. Great. Now what if these individuals are on Metformin for their diabetes mellitus—are you still going to give them your cookie cutter supplement plan and pocket their money? I digress—let me get off my soap box and back to the topic at hand.)

We are going to start talking science here- I’ll simplify it as much as possible, but never will I “dumb down” physiology too much-that is where concepts get misunderstood and “broscience” emerges.

We return to our “lactic acid makes you sore” claim. First, lactic acid is by definition “an organic compound (CH3CHCO2H) which is produced both naturally and synthetically”. It is indeed an “acid” which means it can release a proton (or hydrogen ion, H+). If you have any chemistry background at all you understand that as the concentration of H+ ions increases, the pH decreases. If I lost you at the term “acid” simply understand that a drop in pH levels will affect the muscles ability to continue to contract and contribute to the “burning” sensation you feel in the muscle belly.

When lactic acid releases a hydrogen ion it joins with a sodium or potassium ion to become an acid salt, which we will refer to simply as lactate. Previously held beliefs were that this release of a hydrogen ion would cause a drop in pH coined “lactic acidosis” and decrease the muscles ability to continue to perform work. Recent studies however have shown this not to be the case.

Here is where the “lactic acid” theory has faults. There is little to no biochemical evidence that high levels of lactate CAUSE acidosis, but instead there is CORRELATION between the two. (Not to veer off course too much, but correlation simply means there is a relationship between two items, as “A” increases so does “B” and vise versa. NOW this is not saying that an increase in “A” CAUSES an increase in “B”, but simply that there is a positive correlation between the two. What if there was another factor, “C" CAUSING an increase in both “A” and “B”?) There is no denying that lactate levels increase during intense bouts of exercise, but is that really what’s behind it all? Could it be a separate metabolic process that causes the acidosis affecting performance and causing muscular fatigue during intense exercise?

Studies are now showing this to be the case. In reality lactate serves as a buffer during intense exercise and can RETARD, not cause acidosis (since it can ACCEPT an H+ ion). You read that right- could you have been lied to about lactic acid this whole time?

The belief is long-held and even published in numerous text books- heck- it’s what I was taught through my schooling. BUT upon further investigation and my own inquiry of how lactate accumulation could possibly be the cause of the acidosis I discovered the supporting data is weak at best.

So then what is actually causing the drop in pH that creates the threshold to which you can work without oxygen (anaerobically)? Could it be the breakdown of ATP (adenosine triphosphate) to ADP (adenosine diphosphate) and Pi (inorganic phosphate)? During this reaction, one of the phosphate groups is removed from ATP via hydrolysis releasing a proton (H+ ion) and energy (that of course is a highly simplified explanation of the reaction). Just remember that ATP is our bodies "energy currency", it is what fuels your activity.

When the amount of ATP needed to fuel the activity is met via cellular respiration (think exercise WITH sufficient oxygen), the protons released are used and do not accumulate meaning the pH stays relatively neutral. Now if the need for ATP increases and cannot be met via respiration (for example with intense exercise) two different energy systems, glycolysis (activities lasting about 30 seconds to 2 minutes) and/or the phosphogen system (about 10 seconds of all out work) come into play. Once called upon, these systems can supply ATP but they also increase the amount of protons released in turn lowering the pH to a more acidotic level. Think intense, anaerobic exercise (without oxygen) = proton release= acidosis.

Why then do lactate levels also increase with intense exercise (studies do support this correlation)?

Glycolysis itself breaks down carbohydrate (in the form of glucose or glycogen) into pyruvate. The interesting thing about pyruvate is that it can have two fates. When enough oxygen is present it can be oxidized in the mitochondria to produce more ATP. However, when sufficient oxygen IS NOT present, it will be converted into LACTATE. Notice I did not say lactic acid. So with intense exercise in which oxygen is a limiting factor lactate levels will INCREASE.

Interesting right? Hopefully you now see that lactic acid/lactate are not the cause of your muscular fatigue/that “burning” sensation within the muscle belly. Instead, it is your body working to meet the energy demands of your muscles via ATP production.

Now what about the theory that “lactic acid makes you sore” or the attribution of your DOMS (delayed onset muscle soreness) to lactic acid accumulation. Both of these are again, false.

At rest normal lactate levels in the blood are between 0.5 and 2.2 mmol/L. At complete exhaustion (as seen with intense exercise) they can be as high as 20-25 mmol/L. Peak lactate levels are seen 3-8 minutes after the completion of the activity depending on intensity and training level. A return to normal levels is usually seen within 1 hour of exercise cessation. An active recovery/cool down and regular training can decrease the amount of time it takes for the lactate to be “removed” from the blood stream.

Wait did I just say lactate (or “lactic acid” for all my bros out there) is gone within 1 hour of completing your training? That’s correct. Lactate is oxidized to pyruvate by the lactate dehydrogenase enzyme. Pyruvate can then be used in the Krebs Cycle helping your body produce more ATP (in the presence of oxygen).

This is all good and well but why are you sore after your lifting sessions? Remember, when you are strength training you are ultimately creating “micro-trauma” within the muscle belly. These small “tears” (if you will) are then repaired and built back stronger than before (assuming proper rest and nutrition practices are used.) The muscle can then withstand the same or greater loads in successive workouts. This is how we get “stronger” and why we experience hypertrophy of our muscle fibers.

(Note that eccentric loading, or that applied as the muscle lengthens will create more muscle breakdown than concentric loading which occurs as the muscle contracts. Cool huh?)

This trauma causes the accumulation of byproducts and fluids in the muscle while also increasing inflammation. THIS is what causes the soreness, not an “accumulation of lactic acid”. This soreness often arrives 24-48 hours AFTER the activity and can be referred to as DOMS or delayed onset muscle soreness.

If you pull anything from the last 10 minutes of reading this post may it be that:

1) Lactic Acid does not build up in the muscle, but lactate does (and the two are NOT synonymous).

2) The cause of decreased performance, the “burning” sensation felt in the muscle belly and the inability to continue high intensity exercise for long durations are not related to lactate but other metabolic processes which produce the ATP your muscles are utilizing in turn creating a more acidic environment.

3) The soreness you experience 24-48 hours after your training session is NOT “acid” in your muscle but micro-trauma you have created in the muscle fibers which in turn lead to byproducts/metabolites/fluid buildup and inflammation.

Make Sense? Yet another bro theory put to rest. If your trainer is spouting off about lactic acid, RUN. (Or better yet ask him/her what exactly lactic acid IS and see what crazy answer they come back with. You may now know more than them on this topic.)

As always, be a smart consumer, do your research, check credentials and for goodness sakes, don’t believe everything you hear and read.

Interested in individualized training or nutrition programs or have a burning fitness question? Contact me at lindseymwoodkey@yahoo.com or visit keypotentialfitness.com.