We’ve introduced the body’s energy systems, those complex mechanisms responsible for producing ATP energy, delivering it to the working muscles, and utilizing it to power activity.

If you have NOT yet read the first article in this series that introduces the topic of conditioning and energy systems, I highly suggest you do — it’s an important part of understanding THIS article. The next article covers exactly HOW to Improve Aerobic Fitness for Muay Thai, covering exact training protocols you can follow. But, I suggest you READ this current article first so you know exactly what the Aerobic System is, how it affects your overall conditioning, and why you need to train it.

If you understand HOW the body works from an energy supply and utilization standpoint, you can then put together a custom strength and conditioning program designed to TARGET those specific areas to improve the underdeveloped areas in your own energy systems and push your cardio through the roof.

The Aerobic Energy System: The Energizer Battery


Ever see that Energizer battery slogan ‘It keeps going… and going… and going…’?

Well, your aerobic energy system is your body’s energy producing version of an Energizer battery. It keeps going…and going…and going…

The aerobic system has a tremendous capacity for sustained energy production over a long period of time as compared to the tremendously fast energy production, but quickly fatiguing Anaerobic energy systems.

Most of your activities throughout the day are directly powered by aerobic energy — energy produced by aerobic metabolism.

Here’s a chart showing the contribution of total energy depending on the type of sport/activity:

Event Aerobic energy system contribution Anaerobic energy system contribution
200m 5% 95%
800m 34% 66%
1,500m 50% 50%
10,000m 80% 20%
Marathon 98% 2%
Football-GoalkeeperForwardMid-fielder 20% 100%100%80%


You can see here how for every single one of these activities, your aerobic system is making some contribution. No matter what you do, your aerobic system is contributing some energy to your overall energy output, even for activities that are highly explosive in nature (sprinting). This is why it’s crucial to improve this energy pathway to be more efficient.

Here’s another look at the three energy systems, the long-term energy system (aerobic), short-term energy system (anaerobic lactic acid), and the immediate energy system (phosphagen/ Pcr/ ATP + CP):


It’s important to note that these three energy systems do not operate in isolation but work concurrently together. There’s a lot of research about how these energy pathways still exactly work and still many unanswered questions researchers have. However, even for very short periods of intense activity, your aerobic system makes contributions to your energy output, even though your anaerobic systems are doing most of the heavy lifting. And likewise, even during longer durations of slower energy output where your aerobic system is doing the heavy lifting, your anaerobic systems still kick in SOME energy. See this graph below and you’ll see that all three energy systems make some contribution no matter how high the energy output is per function of time:

energy systems

Why do we call Aerobic Energy System ‘Aerobic’?

We call it ‘aerobic’ because oxygen is a required component in the chemical process that produces ATP via this system. Since oxygen is used as part of the ATP production aerobically, the byproducts of ATP produced aerobically are only C02 and water.

Thus, the aerobic system is limited only by the cardiovascular capability, the oxygen uptake/absorption ability of the muscles, and the number of enzymes and substrates present that are required for ATP production.

All of these elements, through targeted training, can be made more efficient or productive and as a result, increase your aerobic energy production and thus increase your aerobic fitness.

And increase your aerobic fitness and your anaerobic fitness capabilities will also improve.

So because your aerobic fitness affects your anaerobic fitness, the aerobic fitness system is the most important system to start training, especially for new trainees

If you have a well-developed aerobic system already, then focusing on the anaerobic systems may be more beneficial.

What is Aerobic Fitness?

This refers to your energy production that utilizes oxygen to produce ATP which is supplied to your working muscle fibers. Your Aerobic system is what produces MOST of your energy for any activity that is NOT explosive in nature; any activity that requires a constant energy supply of more than 90 seconds starts tapping into your aerobic system to provide energy to the muscles.

This is why activities that require sustained explosive power and high heart rates can only be sustained for about a minute and a half before fatigue sets in (and the body is forced to switch over to the slower energy production of the aerobic system). Think of sprinters, wrestlers, or other sports that require immense sustained power outputs for a short duration.

You can think of the aerobic energy system as your long duration energy supply. Activities like running, skiing, swimming, cycling are primarily powered by your aerobic energy system with explosive bursts tapping into your anaerobic systems.

How does the Aerobic Energy System Provide Energy?


The Aerobic system uses oxygen in the chemical processes used to produce ATP. It’s a slower energy production than anaerobic (seconds to a minute), but capable of producing a lot more energy for a longer duration (hours).

Without getting too much into a chemistry class, the aerobic system can take one glucose molecule and produce 38 ATP molecules (with 34-36 available to the muscles as an energy source).

Compare this to the anaerobic systems which only produce only 2 ATP molecules per chemical reaction and you can thus see why the aerobic system as a lot more ATP-producing capacity. In fact, you could say aerobic metabolism produces 15-16 TIMES more energy than anaerobic metabolism.

You can see why then aerobic metabolism is capable of producing MUCH more energy than the other energy systems and why it’s the major source of all your working energy, especially over a longer period of time.

The Other Energy Systems (Anaerobic Lactic and Anaerobic Alactic)

More on this later…for now we will only introduce the topic of anaerobic energy so you understand aerobic energy better.

Your anaerobic systems consist of the anaerobic alactic system and anaerobic lactic system) can only provide sustained energy for less than 90 seconds before giving out.

Short explosive activities such as sprinting, power-lifting, etc are powered by your anaerobic energy systems because the ATP (the energy source utilized by your muscles) is produced far more rapidly as oxygen is not used for the ATP production and there are fewer chemical processes involved.

Basically, Anaerobic energy production is a HELL of a lot faster with far few steps in the process meaning ATP can be produced and delivered more rapidly to your muscles. Only the anaerobic systems can provide ATP quick enough to fuel explosive high work rate actives (like throwing explosive combinations for a knockout or going balls to the wall for 30 seconds trying to get that knockout).

In the section above, I showed you that your aerobic energy system produces a LOT more energy per reaction with 38 ATP molecules produced from 1 glucose molecule compared to the 2 ATP molecules produced from 1 Glucose molecule by anaerobic metabolism. So the TOTAL energy capability of the aerobic system is many many times more than the anaerobic system.

However, the RATE at which ATP is extracted and produced from that glucose molecule via aerobic metabolism is quite slow — too slow in fact to supply enough ATP if your muscles need it immediately and in large doses at once. Only anaerobic metabolism can supply ATP rapidly enough to meet your muscular energy needs. However, the ATP production capacity is very short for anaerobic metabolism — under a minute in fact compared to the hours of constant ATP production that your aerobic system can supply.

Why is the Aerobic Fitness Important?

Simply put, your aerobic fitness is the foundational fitness on which your entire conditioning is built on.

Any sustained activity without a rest period that’s longer than a minute to a minute and a half will require the aerobic energy system to kick in and supply the majority of the energy (McArdle, Katch & Katch, 1991). If for short durations the muscles require a quicker supply of APT,  anaerobic systems will kick in and fill in for the aerobic system for short periods, but most of the energy outside of this will be from the aerobic system.

The Aerobic system does three important things:

  1. Aerobic System supplies most of your long duration energy (over 90 seconds):
  2. Aerobic System helps removes waste buildup from Anaerobic Systems (reducing and preventing fatigue levels)
  3. Aerobic System resupplies chemicals that fuel the Anaerobic System

Sustained activities that last over 2 minutes will have a higher contribution of energy from the aerobic system.

If your aerobic fitness is not good, your anaerobic fitness will be limited as well. A poor aerobic system will mean it takes longer to remove waste products from the Anaerobic mechanisms and restock the materials needed for anaerobic energy production. That is, if your aerobic system is poor, it will take you longer to recover from explosive uses of energy (which utilize the anaerobic systems)

As such, this aerobic system is incredibly important for both your long duration energy production over the fight and also your short, explosive energy bursts.

The Benefits of Aerobic Training

circuit training

A solid foundational aerobic base is critical to developing good anaerobic fitness. Specifically, aerobic training will bestow upon you the following conditioning benefits:

1. Quicker Recovery After Explosive (Anaerobic) Activity

Good aerobic fitness helps recovery between intense bursts of activity (anaerobic energy) such as after explosive combinations or recovery between rounds.

A strong aerobic system can (more) quickly restock chemicals required by anaerobic energy production.

Your aerobic system is not operating only by itself; it is intrinsically linked to your anaerobic system. BOTH energy systems work together at the same time concurrently in some way.

Thus, your aerobic capacity affects your anaerobic capacity too.

Having a strong aerobic energy system means this system becomes more efficient (faster) at removing fatigue-causing waste products in your muscle fibers produced by anaerobic metabolism and lactate metabolism (recycling the lactate created from anaerobic metabolism back into an energy source by converting it to pyruvate which can be shunted back into ATP via aerobic metabolism in less active muscles) Brooks and Fahey (1985).

This allows for continual explosive exchanges over and over with shorter rest requirements between each series of high-intensity fight exchanges because your aerobic metabolism ‘recharges’ in a sense your anaerobic metabolic capabilities.

Muay Thai application: Think going hard in a fight for 30 seconds, then having the ability to go hard again after a few seconds of recovery time and being able to do this over and over again.

2. Longer Sustained High Power Activities

Sustained activities lasting over 2 minutes have a higher aerobic content. Although primarily anaerobic, a 3-minute round still requires contribution from the aerobic system (Astrand and Rodahl 1986). Those contributions are that the aerobic energy system can (more) quickly remove waste products produced by the aerobic system.

Muay Thai application: removing waste products in the muscle tissues allows helps postpone fatigue buildup in the muscle, meaning longer explosive durations. This directly ties into anaerobic energy system training in which you improve your muscular tolerance of fatigue causing waste product. But know that your aerobic system ASSISTS your anaerobic system in helping to remove waste and resupply the mechanisms that allow or anaerobic metabolism.

3. Improved Anaerobic Threshold

Aerobic training can improve your anaerobic threshold (the point where lactate production exceeds lactate removal and the energy production moves from aerobic metabolism to anaerobic). Basically, your heart rate can be much higher while still utilizing energy from aerobic metabolism.

If your aerobic system is not strong, then you tap into the much quicker fatiguing anaerobic metabolism with a lower heart rate.

A strong aerobic system can utilize MORE energy from the aerobic system with higher levels of POWER output WITHOUT tapping into the quickly fatiguing anaerobic system.

This allows for more power for a longer duration with less fatigue. And that’s a good thing for pretty much any sports activity.

The faster your body can produce ATP aerobically, the less you will have to rely on the more quickly fatiguing anaerobic system and the more fight endurance you will have.

Muay Thai Application: You can throw more strikes per round without fatiguing, thus increasing your WORK RATE during the fight.

So I hope it’s pretty clear at this point how important your aerobic fitness is to your overall conditioning.

Who Should Train the Aerobic Energy System?


In one word, everyone. Ever person who wants a good conditioning base MUST train the aerobic system, at least part of the time. Time can be taken away to train the other systems, but you will still need to maintain a good aerobic fitness base. And if you don’t have it already, then you need to get it.

But I’ll make this more specific.

For new trainees, those who have never done strength and conditioning work, or active fighters who do not have good endurance (even if they have explosive power for short periods), building up a strong aerobic system FIRST will likely give the most bang for the training buck. Once your aerobic system is strong, you can focus on the other energy systems to improve your short term power duration.

But you need the aerobic base first.

Make sense?

Aerobic Fitness is MORE than Just Running


When we talk about increasing aerobic fitness, most people have some idea how to make that happen.

Running, skipping and other classic ‘roadwork’ is commonly used by pretty much every fighter — Boxer, Muay Thai, MMA fighter, Wrestler, etc to increase fitness.

As such, improving your ‘cardio’ has become linked with performing the classic long duration aerobic activities (roadwork) like running and skipping that improve your heart and cardiovascular system.

And this is correct — these activities do build a strong aerobic foundation. Certainly, you could ONLY just do these roadwork activities and your conditioning will dramatically improve.

But while these aerobic fitness activities improve your overall energy production capabilities, they do not specifically increase your muscles’ efficiency at using that improved energy production.

So you see, to get the maximum benefit of aerobic training, we need to ALSO improve your muscular ability to absorb and utilize that oxygen better. And to push these adaptions to happen requires specific training that’s NOT just long duration road work training to improve.

At the end of the day, your muscles are what USE this energy; having more energy to play with is great, but if your muscles (the ultimate users of that energy) can’t process that energy faster and more efficiently, then their limitation will be the weak link in your conditioning chain.

Again, to take our car metaphor, you can increase your gas tank size in your car which can increase how far you can drive, but if you ALSO make changes in your engine to make it more efficient in how it burns the fuel, you can also increase the gas mileage.

So to reap the FULL benefits of building a better aerobic system, not only do you need to increase how much ATP produced (through more oxygen supply, more rapid ATP production) you also have to increase your muscles’ ability to handle the extra ATP being produced.

The Aerobic System and How It Impacts Your Muay Thai

Muay Thai, with 3 minute rounds require a contribution from the aerobic system; even if you go balls to the wall for nearly two minutes, it will be the aerobic system that powers you through at least half of the round and it’s what will help to recharge your ability to be explosive over and over without fatiguing. Between rounds, a well developed aerobic system can aid in your recovery (your heart rate will drop faster during the round breaks meaning you are more recovered for the next round) and provide you with continual steady energy for all five rounds. On the other hand, an aerobic system that’s not well developed will mean you get tired far faster and will not be able to recover quickly after explosive combinations.

Now think about a typical Muay Thai fight. The fighters circle each other throwing submaximal powered strikes, occasionally broken up by maximum strikes. You don’t throw with 100% of everything you have for the full five rounds. Occasionally, fighters will turn the power knob to full and go for a knockout with an explosion of strikes, but these exchanges are always for limited durations before the fighters retreat, cover up or clinch to rest.

Fighters commit the cardinal error of going full power in the first round or two (and failing to get a KO) without budgeting their energy levels for the later rounds are often left completely ‘gassed’ as the rounds progress.

As such, having strong aerobic fitness will enable a Nak Muay fighter to have a high work rate each round over and over, without fatiguing, from round one to round five.

The Aerobic Energy System: The Components

We can break the Aerobic System working parts into three major components: aerobic supply, aerobic utilization, and aerobic substrates.

Now obviously this is a gross simplification for how things work, but for the purpose of a conditioning, it’s a working model.

These three components are impotent to here because each of them, through targeted training, can be improved. Improve one and your aerobic fitness increases, sometimes dramatically.

Indeed, aerobic training can improve aerobic capacity by forcing adaptions to the body’s oxygen supply, transport, and oxygen utilization systems (McArdle et. al., 1991).

1. Oxygen Supply Engine (aerobic supply)

cardiovascular system

We can improve our conditioning by improving the net oxygen supply to the working muscles. To improve our oxygen supply we need to make improvements to our cardiovascular system.

Roughly speaking the Aerobic Energy Supply has three components:

  • Heart Pumps Blood cardiac output (oxygen supply system)
  • Vascular Network Carries Blood (oxygen transport system)
  • Lungs Take in oxygen (oxygen supply system)

Improve the efficiency of at least ONE of these oxygen supply/transport components and you improve your overall oxygen supply capability. And when you improve your oxygen supply capability, your fitness improves.

2. Oxygen Utilization Engine 


The muscular adaptations that occur given the right training stimulus are as follows:

  • Muscle Contractility (how quickly muscles can contract and relax by increasing number and size of type 2 and type 1 muscle fibers)
  • Increase the size of slow twitch muscle fibers (McArdle et. a., 1991).
  • Increase mitochondria in both slow twitch and fast twitch muscle fibers which produce MORE ATP (McArdle et. al., 1991).
  • Increased capacity of the mitochondria to update and process oxygen so more ATP can be produced  (McArdle et. al., 1991).
  • Increase aerobic enzymes availability so muscle fibers can utilize more oxygen for ATP production

If we push the adaptability inside the muscle fibers for increased oxidation (which at the end of the day means we are essentially increasing the working supply of ATP to the muscle tissue), then we can increase the aerobic capacity of the muscles and increase our muscles’ ability to do more work. And this means your fitness improves.

3. Substrate Stores

To produce ATP, your muscle fibers (specifically the mitochondria inside them) mix oxygen with sugars and fats.

The number of sugar and fat stores (these are called substrates) your muscles have can be increased and their efficiency improved.

  • Increase substrate stores
  • Increased efficiency of stores

However, you are not likely to run out of these substrate stores during a fight; your substrate stores can last for hours.

Long distance runners or other activities that require long periods of sustained aerobic activity require increased stores to power prolonged aerobic activity. However, for the most part, Muay Thai is not a long enough activity where your substrate stores will run out; I include it here for completion.

Wrapping It Up

So far, I’ve introduced your Energy Systems in the first article, introducing the idea that conditioning is really just the manipulation of your body’s energy supply and utilization processes to be more efficient.

In this article, I’ve looked at what the aerobic energy system is and how it contributes to the BULK of your energy and why it’s so important for your overall energy production…and therefore your fitness.

Theory class is now over and it’s time for real world application. If you’ve read both articles, you should now understand exactly what we are going to be doing to our aerobic energy system. Now just comes the application of this theory into your Muay Thai conditioning.

If you want to put this into practice in your training, then read my next in the series How To Dramatically Increase Aerobic Fitness for Endless Fight Endurance.

I specifically outline the exact training protocols that will optimize individual areas of aerobic fitness (longer energy capacity, quicker energy production, and more efficient energy utilization) for dramatically improved fight and training endurance with specific training protocols for you to follow.

To really start this highly-specific training, you’ll absolutely need to get yourself a good heart rate monitor because you’ll need to record your heart rate and specifically keep your heart rate within certain rate intervals for given periods of time and intensities (which change depending on what sort of training you want to do). I’ll have some more articles about how to do this in the future.

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  2. McArdle, W. D., Katch, F. I. & Katch, V. L. (1991). Exercise physiology: Energy, nutrition and human performance (3rd ed.). United States of America: Lea & Febiger.
  3. Astrand, P., and Rodahl, K., (1986): Textbook of Work Physiology. Physiological bases of Exercise. McGraw Hill Book Company. New York.
  4. Brooks, G., A., and Fahey, T., D., (1985): Exercise Physiology: Human Bioenergetics and its Applications. Macmillan Publishing Company. New York