Lactate: The Key to Metabolism
The human body needs energy. If you are not getting enough energy from food, then your body will turn to other sources such as fat stores or muscle tissue. However, these two types of stored energy do not provide all the needed energy for our bodies. For example, if you have no access to water, then your body will use up its fat reserves first before turning into muscles and blood sugar levels drop quickly.
In order to get more energy, your body uses a chemical called lactate. Lactate is produced when there is too much oxygen in the blood stream (oxygen toxicity). Lactate is released from cells during exercise and used as fuel. When you run hard or lift weights, you produce lots of lactate.
Your body produces large amounts of lactate because it wants to conserve itself and keep you alive longer while exercising at high intensity.
When you eat foods containing carbohydrates, fats and proteins, your body breaks down the nutrients into their constituent parts. These nutrients are broken down into glucose which is converted to glycogen in the liver. Glycogen is stored in your muscles as long-term energy supply. Your muscles use up most of the glycogen stored within them, but they still need some to function properly.
When you start to do exercise, such as doing sprints, your muscles begin to use up the glycogen stores. If you were to continue doing sprints, then your body would run out of glycogen and fatigue would set in. This is why it is important to consume some kind of sugar during the race itself. The liver takes the incoming sugar and turns it into glycogen and releases it right back into the blood stream to be used by your muscles.
That’s where lactate comes in. Lactate is used for short-term energy. The muscles don’t burn it as a fuel source. Instead, they use it to turn the glycogen into glucose so that the liver can metabolize it and release more glycogen back into the blood stream.
Lactic Acid Fermentation
As far as your muscles are concerned there is no difference between glycogen and glucose. It is only when the liver metabolizes the glucose that it becomes lactic acid (or lactate). This is why your muscles start to burn during anaerobic exercise. It is not because you are using a different energy source.
Instead, it is simply because there is a buildup of lactic acid in your muscles, and this inhibits their ability to contract properly.
It is at this point that we have to talk about the difference between aerobic and anaerobic exercise. Aerobic exercise is any type of exercise that you can sustain for a long period of time. This is because your body can supply enough oxygen to allow your muscles to keep working without the build-up of lactic acid. Anaerobic exercise is any type of exercise that you can’t sustain for a long period of time.
There isn’t enough oxygen to break down the lactate or glucose, and your muscles start to burn due to the lactic acid buildup.
As a general rule, any type of exercise that you can last for longer than about 30 seconds is predominantly aerobic in nature. For example, if you are running a mile, and you can keep up the pace for more than a mile, then you areaerobically fit. If you reach about half-a-mile, then you are anaerobically fit. The more aerobically fit you are, the more oxygen your body can process.
This enables you to access more energy. The more anaerobically fit you are, the more efficient your body is at clearing lactic acid. This enables you to work at a higher intensity for a longer period of time before lactate acid starts to build up in your muscles.
When you exercise aerobically, your body uses more oxygen than it takes in. This creates a slight negative charge on your body. It is similar to a battery that is charged by external means. When you exercise anaerobically, your body has used up more oxygen than it can supply.
This creates a slight positive charge on your body. It is similar to a battery that has used up all of its charge.
The reason for this is because your body wasn’t designed to last forever. There is only so much energy stored in the form of food, and only so much oxygen you can take in. Your body will supply your muscles with oxygen first. This enables you to exercise aerobically for a longer period of time.
Even though it isn’t the most efficient use of your energy, the payoff is that you are able to exercise for a much longer period of time.
As your muscles become more and more depleted of energy supplies, they start to rely more on anaerobic metabolism. First, your lactic acid build-up starts to slow you down. This is because it creates a buildup of positive charge in your muscles, which interferes with their ability to contract. Second, your oxygen debt keeps on increasing.
This further increases your positive charge within the muscles, and starts to interfere with the electrical signaling between the nerves and muscles.
This is why your muscles feel like they are on fire when you exercise anaerobically. The positive charge building up in your muscles causes a sharp burning sensation. This is an unpleasant feeling, to say the least. This is also the reason why you may start to feel tired after exercising aerobically for a long period of time.
This isn’t really due to lactic acid build-up, but rather due to oxygen deficiency.
The reason why you feel more tired after running a mile than after sprinting 100 meters is because it is much harder to supply your muscles with oxygen. Even though the energy demands may be the same or even higher during the 100 meter dash, your body can’t keep up due to oxygen deficiency. This is why high-intensity intervals are much better for you than going at a steady pace for a long period of time.
Your muscles will still feel like they are burning, but the feeling should go away much quicker. Your body isn’t really burning out; it is just supplying your muscles in a manner that creates that perception. The lactic acid buildup is still there as well, it’s just that your body can clear it at a higher rate due to heightened levels of oxygenation.
So how do you get oxygen to your muscles?
10.2 Breathe Better
Breathing is something that you probably don’t think about all that much. In fact, unless you are someone who suffers from breathing difficulties such as asthma, COPD, or a similar disorder, you may not give much thought to your breathing at all.
Just think about how much you do it. You breathe when you sleep. You breathe when you eat. You breathe when you walk and talk and exercise.
You breathe all the time!
Sources & references used in this article:
Pyruvate decarboxylase: a key enzyme for the oxidative metabolism of lactic acid by Acetobacter pasteurianus by KC Raj, LO Ingram, JA Maupin-Furlow – Archives of microbiology, 2001 – Springer
Citrate metabolism in lactic acid bacteria by J Hugenholtz – FEMS Microbiology Reviews, 1993 – academic.oup.com
Carbohydrate, peptide and lipid metabolism of lactic acid bacteria in sourdough by MG Gänzle, N Vermeulen, RF Vogel – Food microbiology, 2007 – Elsevier
Lactobacillus sanfranciscoa key sourdough lactic acid bacterium: a review by M Gobbetti, A Corsetti – Food Microbiology, 1997 – Elsevier