Aerobic Fitness

WHAT IS IT, WHY IS IT SO IMPORTANT AND HOW DO I TRAIN IT?


Over the last few years it’s been popular to bash the importance of aerobic fitness. It seems like we’re told to avoid long slow distance work and that the best way to get ‘fit’ is through high-intensity intervals or something like a CrossFit metcon. People think going for a long-distance run is going to kill your strength gains while making you as skinny as a rake.


In reality, the aerobic system is one of the most efficient and important energy systems with the most room for improvement. Obviously, the aerobic system has the potential to increase your aerobic capacity and aerobic power (as we’ll talk about later), but it also helps the other energy systems in the body recover between efforts. Most sports, especially team sports and individual sports lasting over 2 minutes rely heavily on the aerobic system to provide sustained energy.


The recent hype of high-intensity training has led most of the population to believe that incorporating HIIT with reduced rest periods is the best way to train the aerobic system. And while there is a carryover to developing the aerobic system this way, it’s important not to neglect the other benefits that come from longer, lower-intensity exercise. Only working on your aerobic system in one way (LSD, HIIT, fartlek etc.) won’t allow you to reach your true aerobic potential. So, it’s important to mix up the stimulus, which we’ll explain later.


Before we get into the nitty gritty of all the science. It’s important to understand what we’re talking about.

There are three energy systems within the body that help provide energy allowing us to move. The aerobic system, the anaerobic lactic system and the anaerobic alactic system. Both anaerobic systems require no oxygen and therefore only last a maximum of approximately 2 minutes. They cause negative by-products to accumulate which lead to fatigue or burn out. While these two systems are important in sports and often focused on more than the aerobic system, they both rely on the aerobic system to refuel and clear out the by-products that accumulate when these systems fatigue. We’ll go into more depth on these systems later. But this week we’re focusing on the development of the aerobic system.


All the energy systems create energy through breakdown down of a molecule called ATP to ADP. The aerobic system uses oxygen to do this and it is a much slower process than the anaerobic systems due to the increased number of chemicals and processes. But as I’ve already hinted at, the aerobic system provides energy for the longest amount of time, contributing the most amount of energy in any exercise over 90 seconds or so.

It can also produce energy with very little negative by-products that cause fatigue – hence, why it’s possible for ultra-marathoners and Ironman athletes to compete for hours or even days on end. This means that the aerobic energy system is only limited by oxygen supply, our muscles ability to utilise that oxygen and enzyme availability (which we call substrate availability). The aerobic system is also the only system that can breakdown fats which is useful for endurance events and general activities of daily living.

There are two main areas in which to think about the efficiency of your aerobic system:


1. Aerobic power: how FAST you can produce energy using the aerobic system

2. Aerobic capacity: how MUCH energy you can produce using the aerobic system


Both things have their benefits when it comes to sports performance and depending on your sport, one may have more impact than the other. For example, a marathon runner competing for 2+ hours is going to rely a lot more on aerobic capacity as they don’t need to produce energy as fast. While an MMA fighter, fighting 3x5 minute rounds, will need to produce that energy (mostly aerobically) at a much faster rate.


And as I said earlier there are three main areas we are looking to improve when training the aerobic system:


1. Oxygen Supply

How good your heart, lungs and blood vessels are at delivering oxygenated to the muscles and carrying de-oxygenated blood away from the muscles. Here we are looking to increase our cardiac output (by increasing the size of the hearts chambers or how hard they can contract).


2. Oxygen Utilisation

How well your muscles use the oxygen that’s delivered. I’m sure most people are aware that the muscles in your body are made up of fast and slow twitch fibres. Slow twitch fibres rely on oxygen to fuel them and create energy at a slower rate, but for longer. While the fast twitch fibres are bigger and more powerful, they fatigue faster. They can create energy with or without oxygen present. So, while people may use the excuse ‘I’m fast twitch dominant and can’t run for very long’ it’s important to understand that you can absolutely increase the endurance capabilities of fast twitch fibres as well as making them bigger, stronger and more powerful. Regardless of the type of fibre, we want to increase the number of mitochondria (energy production using oxygen) and enzymes (help in the chemical breakdown of ATP, fats, sugars, etc.) in the cell.


3. Substrate Availability

The amount / capacity of fuel (in the form of stored sugars and fats) and enzymes available to efficiently breakdown ATP with oxygen. Running out of stored fuel will cause you to ‘hit the wall.’ This is more important in endurance / ultra-endurance events but can still be important for team sports that go for extended periods i.e. AFL. The better your endurance training, the better you are at storing and using these fuels.


Developing one or all of these pathways will go a long way in optimising your aerobic energy system. Therefore, it’s important to train the aerobic system in a combination of different ways (which we’ll go through soon). Avoid choosing purely HIIT or long-slow-distance. If you only train your aerobic system in one way, there’s a good chance that you’re not reaching your potential.


So how do we improve our aerobic system through training?


Here’s 5 different training strategies you could incorporate into your program to ensure you’re ticking off each of the 3 factors mentioned above that lead to a more efficient aerobic system; oxygen supply, oxygen utilisation and substrate availability. *Note: Joel Jamieson discussed these methods in his books Ultimate MMA Conditioning. This is known as one of the best books on energy system development for anyone interested in the subject.


1. Long-slow distance work


This method works on increasing stroke volume. Stroke volume = how much blood is pumped per beat. It does this is by increasing the size of the left ventricle which increases the total volume of the heart. More volume in the left ventricle equals more blood that can fill the heart between beats. Therefore, you can pump out more blood with each beat. If you can pump out more blood each beat then your heart doesn’t have to beat as many times to get the same amount of blood around the body (decreasing resting heart rate). Reduced heart rate means you can do MORE work for LESS effort (increase in cardiac efficiency). Note that if you train too hard, and increase your heart rate too high, you will start to get a different adaptation (discussed in the next point), so ensure that you keep heart rate to the recommended range below.


Here’s some guidelines to follow:

· Aim to train with a constant heart rate between 120-150 (I’d stay below 140bpm)

· Do this for 45-90+ mins

· Increase volume at or less than 10% each week i.e. 50 mins week 1, 55 minutes week 2.

· This can be done with running, cycling, swimming, assault bike, rower, ski erg or any other type of cardio where you can maintain this heart rate for extended periods.


2. Long high-intensity intervals


Rather than forcing your heart to stretch out and increase in volume like the LSD work, this method works to increase the thickness of the cavity wall and therefore its ability to contract more forcefully. Much like strength training increases the size of your muscles, these high-intensity methods work to increase the size of the muscles in your heart. The result is similar however, in that the result is an increase in stroke volume (how much blood can be pumped per beat). At higher heart rates, the strength of the heart is more important, as the time between each beat reduces, which reduces the potential for the heart to fill between beats. A stronger, thicker heart also increases the number of mitochondria in the heart’s tissue, which helps your endurance at high heart rates.


So how do we train for this?

· Intervals of 1-2mins x 4-12 sets depending on duration of intervals and training age

· Rest for 2-5mins

· Heart rate should be pushing maximum above 150bpm

· This can be done with running, cycling, swimming, assault bike, rower, ski erg or any other type of cardio where you can maintain this heart rate for extended periods.


3. Anaerobic threshold work


This method works to increase maximum rate of aerobic energy production. It does this by training at your anaerobic threshold a.k.a. the absolute limits of aerobic energy production without sliding into the anaerobic system. Through this kind of training the contractile properties of your slow-twitch fibres are enhanced and the total number of aerobic enzymes increases. It’s quite difficult to figure out your anaerobic threshold without lab testing. For this training to be most effective, you want to remain within 5 beats per minute either side of that number. However, you can determine an approximate anaerobic threshold through a few different ways. One way to do it is to run as far as you can in 30 minutes. Use the average heart rate and / or pace for the last 20 minutes to find your anaerobic threshold. It’s not perfect but it’s better than nothing. You could also find other methods on the internet and different calculators for 5k race times etc. But this one seems simple.


Training for this involves…

· 2-5 sets of 3-10 minute intervals depending on duration of intervals and training age

· Keep heart rate within +/- 5bpm of anerobic threshold.

· Rest 1-5 minutes between sets

· This can be done with running, cycling, swimming, assault bike, rower, ski erg or any other type of cardio where you can maintain this heart rate for extended periods.


4. High-resistance intervals


These intervals work on increasing the endurance of your fast twitch fibres. This method will increase how effective your muscles are at utilising the oxygen. In this form of training you will be completing intervals focused on low speeds but high resistance. This way we recruit the fast twitch fibres (due to the high-resistance) and force them into increasing their number of mitochondria and therefore, their ability to maintain high-power outputs for extended periods.


We train this system by:

· Performing 15-20 reps (10-12 seconds per rep) at maximal intensity

· Rest until your heart rate is back down to 130-140bpm

· This can best be performed sprinting up a steep incline, with sled pushes / drags, or on a spin bike at a very high resistance.


5. Strength training for slow-twitch fibres


This method also works to improve how our muscles utilise the oxygen in the working muscle. This method is different to the previous however, as it targets the development of slow twitch fibres. Our aim is to stimulate a hypoxic environment (low oxygen) which causes our fibres to grow. By increasing their size (cross-sectional area) we increase their oxidative capabilities, allowing us to create more energy using oxygen. For endurance athletes the bigger your slow-twitch fibres the better. And for team sports or sports completed over a shorter time domain it’s also important to increase the CSA of slow-twitch fibres. In doing so they indirectly improve the endurance of fast-twitch fibres by helping prevent fatigue as well as delaying how early we start producing energy ANAEROBICALLY.


How do we train this?

· Strength training exercises focused on the major compound lifts: squats, deadlifts, RDL’s, push-ups, pull-ups, overhead presses etc.

· Control the tempo for 2-3 seconds on the way up and the way down

· Do 3-5 sets of 8-10 reps on 3-5 exercises


These methods are not the only ways of increasing our aerobic fitness (and Joel goes through more in his book) but these are a good starting point. We haven’t even touched on nasal breathing and other breathing strategies, but that will all be covered at a later date.


As I mentioned earlier, the current craze in strength and conditioning is to bash aerobic training and focus more on the strength and power side of things. While the strength and power are extremely important, we shouldn’t brush aerobic training to the side. Aerobic fitness helps set the foundation for the other energy systems in the body as well as helping you recover faster between your strength/speed/power training days.


If there’s one thing to take away from this article it’s this; the aerobic energy system is extremely important for energy production and your ability to recover between explosive efforts and training it is more complex than doing HIIT or LSD work alone – aim to train the aerobic system across multiple intensities and time domains as discussed in this article for the best results.


If you feel like you’re lacking aerobic fitness or you’d like some specific guidance on how you can best incorporate it into your training, please don’t hesitate to contact us. #one22

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