Zone 2 Training: The Missing Link in Your Cardiovascular Fitness
Zone 2 training isn’t sexy.
There, I said it.
For most people, plodding along at a leisurely pace and concluding your cardiovascular workout only a little out of breath is a much less attractive prospect than blasting a high intensity Tabata session and finishing in a pool of your own sweat.
But as the old parable goes:
“The wise man built his house upon the rock”.
I’ve mentioned previously that one of my goals since starting this Health Room journey has been to slow down a little, and gradually rebuild my body instead of constantly breaking it down.
Alongside mobility and down-regulation, that’s where this long duration, low intensity aerobic work – aka zone 2 training – has come into play.
Let’s get it clear:
I’m certainly not against high intensity training, and it definitely has a number of benefits.
But in this article I want to highlight the equally important role of zone 2 training. Not just in promoting health and longevity, but in establishing a strong underlying aerobic base for athletic performance.
I’m by no means an expert on cardiovascular training methods, but whether you’re an aspiring triathlete or a weekend warrior, hopefully you’ll find something useful below that you can apply to your own training regime.
- Our training (and everyday living) can be split into ‘training zones’, which reflect our level of exertion based on a percentage of our maximum heart rate.
- These zones range from zone 0 (at rest or sedentary) up to zones 5-6 (nearing maximum intensity).
- There’s a growing trend where we spend a lot of time either sedentary (zone 0) and then small periods of time going balls to the wall with high intensity training (zones 3-6), but not much time in between.
- Whilst there are numerous benefits to high intensity work, there are specific benefits that we get from zone 1-2 training that we can’t get elsewhere.
- A solution – increase the amount of time you spend in zones 1-2 by adding in daily walks, building a standing workstation, taking regular movement breaks, and going for a long hike/run/swim every few weeks.
- Ideally, you would build this aerobic base with zone 1-2 work before adding in higher intensity work, but this isn;t always practical for everyone.
Back to Basics: Heart Rate Training Zones
Before we get stuck into the nitty gritty of zone 2 training and what-not, let’s go over some basic definitions:
To get our bodies moving, we need to transform our energy stores into a usable form of energy, and we do this by utilising three different energy systems:
- Phosphocreatine (PC) or alactic system
- The lactate system
- The aerobic system
These energy systems contribute different amounts towards re-synthesising the compound Adenosine Triphosphate (ATP), the ‘energy currency of our body’ – essentially the only source of energy our body can use for work.
The main energy system we utilise depends on the intensity, type, and duration of exercise being performed, as well as the fuel sources available and the fitness levels of the individual.
Aerobic vs Anaerobic Energy Systems
The PC and lactate can both be termed anaerobic – meaning they work without the use of oxygen.
If we use early man as an example, he would be working anaerobically during high intensity, high stress situations, like doing battle with or sprinting away from wild predators.
The PC system is used over very short time periods, typically around 8-10 seconds of very high intensity work. After this, its capacity is exceeded and the trusty lactate system takes over.
We typically find ourselves using the lactate system during high intensity activities that last longer than about 8-10 seconds. It’s great at providing a quick supply of energy, utilising glycogen as the predominant fuel source. As the name suggests, a by-product during ATP re-synthesis is lactic acid, which builds up in the muscles causing muscle pain and fatigue – that all too familiar ‘burn’.
The aerobic system on the other hand utilises oxygen, and is used mainly during longer distance, lower intensity work (but also contributes somewhat to activities that are short and intense).
The caveman would be using the aerobic system all throughout the day as they travel long distances and carry out everyday tasks. Like the lactic acid system it uses glycogen as a fuel, but also starts to use our body’s supply of fats.
Energy Zones and Thresholds
As you can see from the diagram below, our exercise intensity can be split into distinct training zones based on a percentage of your maximum heart rate.
Zone 2 is usually the lowest intensity zone used in training. Zone 1 is typically more recovery work and everyday living (think a basic mobility or stretching routine), and I refer to resting/being sedentary zone 0. As the intensity of exercise increases and your heart rate rises, you begin to ascend through the zones.
These zones correlate with the energy systems we mentioned earlier.
An energy threshold represents the point at which one system is taken over by another as the predominant system to provide the re-synthesis of ATP.
The aerobic threshold occurs when the intensity of your exercise starts to take you into the anaerobic zone, and lactic acid concentrations start to rise. Although it may vary depending on the individual, this generally starts to occur at around 65% of your maximum heart rate, but we’ll look at this a little more closely later.
Zone 2 work (and potentially some low zone 3 work) is predominantly under that aerobic threshold, working the aerobic zone.
The anaerobic threshold is reached when the build up rate of lactic acid in your bloodstream is much faster than the removal rate, and you reach the onset of blood lactate accumulation.
That’s when things start to get pretty painful, and you’re forced to lower the intensity.
Being anaerobic in nature, the higher zone work (3, 4, 5) will usually have you touching that threshold on a pretty regular basis, which is partly why it’s so attractive to a lot of people.
You’re literally pushing your limits…
A Paleo Perspective on Energy Zones
Let’s hold up and take things back a few millenia:
As cave dwellers we would probably be spending the majority of our time in the aerobic zones 1-2.
Our ancient ancestors would have been physically active all throughout the day – walking, climbing, playing, running, climbing, gathering…
High intensity work would be dispersed in between now and again (zones 3 and higher), to catch food or run from predators. But the bulk of your time would be spent in that aerobic zone.
That’s kind of how I like to approach that balance between aerobic and anaerobic work – lots of low level activity throughout the day, with a few high intensity cardiovascular and strength training sessions thrown in throughout the week.
So for example:
I’ll spend the day standing and moving around at my standing desk, with regular breaks thrown in to do light bodyweight movements, short walks, mobility work, and moving meditation.
Then at some point in the afternoon or evening I’ll do a HIIT session or strength training.
The BIG problem with the way many training programs are set out:
We do the strength training and HIIT work, but we forget to move in between…
We do a lot of zone 0 work (sitting at work, in the car, and infront of the TV) and small amounts of zones 3-6 work (lifting weights, HIIT training), but not a lot in zones 1 and 2.
Not only is it making us sick (regular movement is a key factor in longevity), it also hinders our athletic performance. Zone 2 work underpins and improves the efficiency of higher intensity work. By skipping it, it seems that you’re cheating yourself.
Zone 2 Training: Modern Day, Long duration, Low Intensity Aerobic Training
As well as regular old physical activity throughout the day, we can also specifically train to make adaptations in zone 2.
So the goal with zone 2 training is to exercise at a pace that allows you to sustain your heart rate just below the aerobic threshold for a prolonged time period. So that would be a heart rate of around 65% of your maximum (we’ll look at how you can calculate your personal training zone later in the article).
This could be in the form of walking, running, swimming or biking; even sports specific drills like shadow boxing or dribbling with a football.
Whatever you like, as long as your heart rate stays around that aerobic threshold and you don’t cross into the land of lactic acid.
At this effort, it’s thought your body will best be able to make the physiological adaptations to improve your aerobic endurance.
Some of the biggest adaptations from aerobic work are cardiovascular in nature:
- An increased stroke volume, the amount of blood your heart can pump out in one contraction. This is due to an increase in the volume of the left ventricle in the heart, also resulting in a higher cardiac output and lower resting heart rate.
- Increased blood plasma volume, which subsequently increases stroke volume, oxygen transport, and VO2 max – the maximum amount of oxygen your body can utilise in a minute.
Aerobic training also causes metabolic adaptations:
- Increased mitochondria density and size results in more efficient oxygen transportation, along with changes in enzyme activity; increasing the body’s capability to generate ATP aerobically and allowing you to sustain a higher percentage of your aerobic capacity without the build up of nasty lactic acid.
- Despite spending little time in the high intensity heart rate zones, you already have that capability to improve there, and also to recover back to zone two more quickly after bursts of higher exertion.
- Potentially increased oxidation of fat during rest and sub-maximal exercises, allowing you to use fat more efficiently as a fuel and preserve your glycogen stores for use during more intense bursts of activity.
- Aerobic training can also bring your body into a more parasympathetic state; decreasing your sympathetic drive and allowing you to rest and recover more effectively.
Other adaptations include favourable changes in body composition, increased endurance performance, and psychological benefits.
Some people argue that aerobic training is not sports specific, but with the exception of a few athletic events, no sport is purely anaerobic. The majority of athletes could benefit from including some aerobic work.
I agree that when training for some sports such as MMA that rely largely on the anaerobic systems, you should be spending the majority of your time leading up to competition working anaerobically; but ideally this would only be introduced once that aerobic base has been established.
Another common misconception is that this type of training causes you to lose strength and makes you slow.
If all you’re doing is aerobic training everyday over a long time period, then your body will adapt to accommodate that. Your type 2a muscle fibres will become more efficient at performing aerobic work. But changes to your body don’t happen overnight. Mixing aerobic work in with strength, flexibility, and later anaerobic training will help you become a well-rounded athlete and human being.
The major turnoff for most people with low intensity aerobic training is the time it takes. Many people simply don’t have 5 hours to head out on the bike or a couple of hours to spend running after work. It’s often a long slog, and can sometimes be frustrating.
That’s why I mentioned above incorporating low level activity throughout the day as a more realistic alternative for most people.
You could argue that higher intensity training is much more efficient, you can get a lot more done in a shorter amount of time, but it’s personal preference and you’ve gotta weigh up the advantages and disadvantages, which we’ll come onto shortly…
High intensity Anaerobic Training
There are many different methods that can be used within anaerobic training; at the moment high intensity interval training seems to be one of the most popular.
Generally, anaerobic training sessions are shorter and more intense than aerobic sessions, and you’ll spend most of your working time above the aerobic threshold, with periods of rest in between periods of work.
The predominant adaptations that can be seen with anaerobic training include:
- Increased resting levels of ATP, creatine and glycogen.
- Thickening of the wall of the left ventricle in the heart.
- Increased muscle mass and bone density, along with an increase in muscular strength, improving speed and power.
- Improved activity of enzymes that control that control the anaerobic phase of the breakdown of glucose as a fuel source, particularly in fast twitch muscle fibres.
- Increased capacity to generate high levels of blood lactate during all out exercise, possibly due to increased levels of glycogen and an increased motivation to tolerate pain. This allows you to work at a high intensity for a longer duration.
As we can see, although many of these adaptations are beneficial, they’re quite different in nature to those seen with low intensity aerobic training.
There’s definitely some crossover, but there are subtle differences too.
Training anaerobically may increase your speed and ability to tolerate higher intensities for longer periods of time, but training aerobically increases the efficiency of your cardiovascular and respiratory systems, allowing you to work at a higher intensity without having to resort to using the anaerobic system. This preserves your glycogen fuel, and potentially puts lets stress on the central nervous system, which from my experience takes more of a battering than with lower intensity zone 2 training.
Some people like to bring up the 1996 Tabata study; stating that it shows that training anaerobically actually breeds greater results in endurance and fat loss compared to steady state aerobic training.
If you look a little closer though, you’ll see that the ‘anaerobic’ group in the study also performed a total of 70 minutes steady state aerobic work per week. The intensity of the anaerobic exercise was also extremely high, with subjects exercising at 170% of their VO2 max. When most people claim they are performing ‘Tabata’ workouts, they’re often not even getting close to that intensity…
The Potential Risks With Anaerobic Training
Although anaerobic training is definitely a great tool, using it incorrectly or introducing it too soon into an exercise program can sometimes do more harm than good.
Excessive training intensity and abrupt changes in training volume significantly increase the risk for injury to bones, joints and muscles. Obviously low intensity aerobic training also brings with it some risks. If your form is poor, those reps add up over a long run and can lead to overuse injuries. But the same can be said for high intensity work (and the risk of injury may be higher due to increased force production).
If not managed properly, excessive anaerobic training can encourage the body towards an acidic state, potentially due to the excess build up of lactic acid. This acidic environment is associated with inflammation and an increased risk of many chronic diseases.
Overtraining can also become an issue, with associated alterations in neuroendocrine and immune functions. This can be a slippery slope, leading to chronic fatigue, poor exercise performance, frequent infections, and a general loss of interest in training.
The Infamous Grey Zone
Another big issue we see in the health and fitness world is this:
People go too hard on their easy days, and too easy on their hard days.
They’re forever training in the ‘grey zone’ of no improvement.
The training intensity is not low enough to get the benefits of zone 2, but not hard enough to induce significant anaerobic adaptations.
Always training this way leaves you with one mediocre speed, and takes your body to a state where it’s never rested enough to go hard when you really need it too.
I have definitely experienced this myself. Years of combining high intensity and grey zone training with inadequate rest has no doubt contributed towards some of the health issues and injuries I’ve faced.
So along with focussing on my core strength and flexibility, I’m now exploring the more laid back aerobic training approach to build my body back up, before I jump back in to the intensity of martial arts.
How to Calculate Your Zone 2
If you’ve decided upping your daily movement quota isn’t enough and you want to engage in some focused zone 2 heart rate training, we’ll now take a quick look at how you can calculate your aerobic threshold and get you started with the basics.
If you have the time and money and want a real accurate measurement, you can go to a fancy lab and take a blood lactate test; where you are hooked up to a heart rate monitor and samples of your blood are taken as you exercise with increasing intensity until failure. You can then perform calculations to find the exact training zone for you.
Failing that, you can do some basic calculations to get a more approximate value. I personally used this version of the ‘Maffetone Method’, which is quite accurate and pretty simple to work out.
- First, subtract your age from 180.
- Modify this number by selecting among the following categories the one that best matches your fitness and health profile:
a) If you have or are recovering from a major illness (heart disease, any operation or hospital stay, etc.) or are on any regular medication, subtract an additional 10.
b) If you are injured, have regressed in training or competition, get more than two colds or bouts of flu per year, have allergies or asthma, or if you have been inconsistent or are just getting back into training, subtract an additional 5.
c) If you have been training consistently (at least four times weekly) for up to two years without any of the problems just mentioned, keep the number (180–age) the same.
d) If you have been training for more than two years without any of the problems listed above, and have made progress in competition without injury, add 5.
Performing this quick calculation will give you your heart rate in beats per minute, corresponding approximately to your aerobic threshold.
You should start your training session with a warm up of about 10-15 minutes, working at around 10-20 bpm lower than your aerobic threshold value. Your exercise time should be spent hovering 0-10 bpm under that aerobic threshold. You should then cool down at a similar heart rate and time frame as your warm up, but with decreasing intensity.
You’ll sometimes hear this type of training called ‘Zone 2’ training, as it corresponds to the second of Joe Friel’s training zones, a different calculation method that he developed that works by approximating your lactate threshold. Feel free to check it out if you like.
When starting out, the main thing that most people find difficult with this low intensity Zone 2 training is that it just feels too damn slow. People want to feel like they have really worked hard and got the most out of their workout, but sometimes you’ll finish a session without even breaking a sweat.
This is where patience and perseverance comes into play. Sometimes we have to check our ego, slow down, and learn to walk before we run…
So where does high intensity, anaerobic work fit in?
It depends on your training experience, your eating habits, your time constraints, and your personal goals.
From a geeky training perspective, one fairly popular opinion is that you should only introduce anaerobic work when your maximum aerobic function begins to plateau, and this can be determined using the Maximum Aerobic Function (MAF) test, described here.
For example, if you performed this test every month, and for the past 3 months you saw no change in your MAF, you could assume it would be safe to add some anaerobic training into the mix.
But then you might not have the time or will to spend hours in zone 2 every week.
As I mentioned earlier in the article, a combination of lots of zone 1-2 work during the day (walking, taking the stairs, standing at a desk, taking regular movement breaks) in combination with a few long walks/runs and high intensity sessions each week might be the most realistic way to go if you’re looking for balanced, functional fitness and longevity.
Over to You…
A common occurrence is that someone who is perhaps looking to quickly lose weight or begin exercising for the first time will see high intensity anaerobic training as the answer. They see the training schedule of their favourite athletes and try to emulate them straight off, with little or no prior exercise experience, no base.
Regarding the level of exercise level selected, more doesn’t necessarily always produce greater or faster results, and can actually cause more harm than good. You can’t really do any significant damage by training too easily, but you can by training just a little too hard.
Yes: high intensity training sounds much cooler and it may seem that you can get more done in a shorter timeframe. No doubt, it’s definitely a valuable tool.
But the training adaptations are not exactly the same as those found with low intensity aerobic training.
For me, it makes sense that to achieve optimum health and to fulfil your athletic potential, it is safer to lay the foundations working in the aerobic training zone, then build upon this by working anaerobically.
Building the base of your pyramid as wide and solid as you can, in order for the top to be as strong as possible.
I may have botched that quote completely, but I think that sums it up quite nicely.
What are your thoughts on the zone 2 training debate? Let me know in the comments section below!
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