Vo2 max, lactate, zones and energy usage

When I was training for my second marathon, I wanted to develop my understanding and prepare myself for such a long distance. My running pace and fueling techniques had to improve, so I began to read a lot regarding training zones and training the body to be more efficient at a lower intensity.

Zones and Heart Rate

An individual’s heartbeat is used to measure the intensity of an effort that the body is subjected to and can be monitored using a heart rate device such as a watch.  Heart rate can be split up into five different zones, which are a percentage of your maximum heart rate.

A simple way to find your maximum heart rate is to run at your maximum effort for a short distance such as a race (3-5km) and record your BPM (beats per minute).  By taking your maximum heart rate, you can work out roughly where your zones are.  I say roughly, as everyone is different and the percentages will vary from person to person. There is also a probability that you may not even reach your maximum as we do sometimes hold back a bit.  I think it also comes with race experience to know when you have put your maximum effort in. There are only a small handful of 5k races I think I really put my maximum in.

VO2 Max is your absolute maximum (100%), and it is a measurement of the maximum oxygen volume that your lungs can consume at once.


Above is a rough idea of the percentage of each zone.  The percentages will, however, be different for everyone based on your fitness and running experience.


We can represent these five zones with specific events that expect a different level of effort. Zone 1 would match the kind of effort expected for a marathon or ultramarathon distance.  It would be a slow pace that you can happily keep up for several hours.  Zone 5, on the other hand, would be a much faster pace that you can only keep up for a very short amount of time such as a 100m sprint.


The table above gives a rough idea of the kind of events that match each zone based on the normal effort level.

Something to keep in mind when looking at zones is that they are very personal and you can not compare your zones to someone else who has a different level of fitness.  Several different things can factor into someone’s zones including, age, sex, and fitness level.  Comparing a marathon runner and sprinter will produce different results for each zone.

You should consider having a lactate and VO2 Max test if you are interested in having a more accurate set of zones created that is specific to you.  I will cover this test further down the page.


Zones and Running Pace

As explained above, heart rate and the zones associated with an individual’s maximum heart rate are a measure of effort.  Everyone’s level of effort is going to be different based on their fitness and several other factors.  These zones can also be paired up with a set of speeds that a person can run at for each level.  Each person will perceive the same speed differently depending on their fitness and where it falls in their zones.

As an example, let’s take a 5min/km pace and compare it to two different individuals.  A 5 min/km pace would result in a 10km distance in around 50 minutes if it were flat.  For the below-average runner, this kind of pace would be considered a challenge and may fall around the zone 3 or 4 level of effort. On the other hand, an experienced runner may find this kind of pace relatively easy and around their zone 1 or 2.  For the experienced runner, their equivalent zone 3 effort would maybe be a 4 min/km pace.

You can roughly work out how different running speeds (pace) relate to your heart rate zones by comparing recent results from races or training runs. A simple method would be to record your maximum heart rate over a short distance.  You can then work out your rough heart rate percentages from this maximum.  On following runs, you can record what kinds of pace you run at for each zone.   This will give you a rough indication what the best pace is to train at for different events based on the table of events above. This doesn’t mean you can’t run faster in the race though! Example below.


The following chart is an example of a basic profile that you could work out at home.  If your Maximum heart rate was 185 BPM in a recent track workout, you could then use the percentages above to work out your heart rates for each zone.  You could then go for a run and record your pace for each heart rate.  You can then match the pace for each zone to a particular running distance.


Something to consider is that as you train in your set zones your fitness will improve and change the zones, which will require you to re-test yourself every 15 weeks roughly.

Energy usage and zones

The body uses two primary sources of energy, fat, and carbohydrates (glycogen from muscle reserves or glucose in the blood) that are employed in different amounts based on how hard the body is working.

When the body is working at an effort level of zone 1 or below, it prefers to generate most of its energy using oxygen and fat, which is known as the aerobic system.  Fat is something we all have an abundance of in our bodies, but it takes the body a lot longer to break down and turn it into fuel.  If you stay at or below zone 1, you can survive without any additional carbohydrates for a substantial period, which is an ideal zone to run at for an event like a marathon.

When we cross from zone 1 to 2, we are also crossing the aerobic threshold and switch from the aerobic system to the anaerobic system.  This is where the ratio of fat to carbohydrates usage switches and the body primarily uses carbohydrates since it’s a more accessible form of fuel.  As the effort level increases the amount of fat used drops considerably to the point, none is used at all.

The body only has a limited supply of carbohydrate reserves and then requires consumption of them to maintain the same level of exertion. The term hitting the wall or bonking is the point in a race or hard effort that the body runs out of these simple sugars and begins to shut down so you can revert to your aerobic system to use fat again.


When considering a race, you should factor in how running in a different zone will affect the type of fuel you will burn and ability to run the distance you have chosen with the right fuel.  A lot of people end up running above their zone 1 in a marathon and switch to an anaerobic system, which will leave them depleted in carbohydrates and find themselves ‘hitting the wall.’  When dealing with shorter distances you can rely on your reserves and take in simple sugars like gels.



Lactate (lactic acid) is the by-product of the chemical reactions taking place when carbohydrates are used for fuel as part of the anaerobic system.  As someone’s effort increases the amount of lactate begins to build up in the system and muscles.  As this increases the body finds it harder to clear this build up and causes a burning sensation that forces you to slow down or stop.  The lactate threshold (or anaerobic threshold) is the point at which the level of lactate begins to build up more than the body can clear it.  This threshold is roughly around zone 3 and zone 4, which is partly why you can only run in your higher zones at shorter events.


Aerobic and Anaerobic Thresholds

With the correct training, it is possible to teach your body to clear lactate more efficiently giving you the ability to raise your anaerobic threshold.  Running at a zone 3 pace will help do this.

The same theory works with your aerobic threshold.  By running at or below your aerobic threshold (zone 1), you can gradually push that threshold up.  By raising these thresholds, you will begin to run faster at the same effort.

By increasing these thresholds, you will start to run faster at the same effort.  You will also affect your maximum ability and zone percentages.


Training Efficiently with zones and thresholds

By understanding your unique zones and thresholds, you can be very specific with your training for an event.  Knowing your pace in each zone will allow you to run at the correct speed to raise each threshold accordingly.

If you were, for instance, training for a marathon, you would want the majority of your training to be around your zone 1 pace since this would be the preferred speed for this kind of event.  You will gradually increase your aerobic threshold in this area allowing you to run faster with less effort. By training in zone 1, you will also train your body to use fat as a primary source of energy, so you don’t deplete your carbohydrate reserves.

There is, however, only so far you can raise the aerobic threshold before your anaerobic threshold gets in the way of expanding your zone 1.  For this reason, it is also good to work a little at your zone 3 pace so you can raise this too.

If you prefer the shorter distances then the majority of your training may be just below your anaerobic threshold so you can train the body to clear lactate more and be able to run faster.  Similarly, it would also be good to train in a higher zone (zone 5), so your anaerobic threshold isn’t held back by your VO2 max.

I would highly recommend having a VO2 max and Lactate test performed to work out exactly where your heart rate zones are, along with your aerobic and anaerobic thresholds.  Having an accurate profile will make your training far more precise and efficient.


Heart Rate training

When going for a run, you may just go by ‘feel’ either for a set amount of time or a set distance.  On the other hand, you may run at a set pace indicated on your running watch or phone.  Another common method is running at heart rate.

So what is the difference between training by heart rate and pace? As I have mentioned in this post, heart rate is a measure of effort.  If your aim is to train for a certain zone then sticking to a set BPM will be a far better method than pace.

Here is an example why. Let us say you are sticking to your zone 1 during a long run as you are training for a marathon.  Your target heart rate is 147 bpm, and this may equate to a 6 min/km pace on a flat trail  You then come to a hill with a steep incline.  To run up the hill at a 6min/km pace will be quite difficult and this will push your heart rate and cross over to an anaerobic zone.  If your target is to stay in your zone 1, then you can monitor your BPM and slow down as you go up the hill to avoid raising it. It may even require you to walk the hill to stick to your zone. Over time this training will further improve your aerobic ability to the point you will be able to run the hill at 147 bpm and the same 6 min/km pace.

Heart rate can be affected at times from to stimulants such as caffeine, heat, how tired you are, and nerves.  It is always good to give some buffer (5 bpm) below your target heart rate to allow for any changes in how you are feeling or external factors.

Heart rate training is best suited for zone 1 and 2 while training your aerobic system. As you increase intensity and train in zones 3 or above it’s much harder to get an accurate heart rate reading as there is quite a slow response to a change in effort and heart rate compared to the change in speed.


VO2 max and Lactate testing

As I was training for the marathon, I began to look into the effects of running by heart rate rather than by pace. I noticed over a few months that I was running consistently at roughly 154bpm each time and my pace was slowly increasing as I improved my aerobic threshold. I knew I could go more in-depth with this type of heart rate training and have a very accurate profile created by having a VO2 max and lactate test performed.

The test involves the athlete running on a treadmill and every three minutes the speed gets increased by 1kph until you can’t go anymore.

A snorkel-like device goes over your mouth that records the amount of Oxygen consumed and Carbon dioxide exhaled during the different efforts. This helps to determine your VO2 max but also the amount of fat and carbohydrate that is being used at various intensities.  This type of data helps an athlete work out exactly how many carbs they require per hour of exercise at different intensities.

Heart rate and a blood sample are taken every three minutes before the speed is increased to measure and plot the lactate build up over time and change in the intensity. The aerobic threshold always occurs when lactate reaches 2.0 mmol/l and the lactate threshold occurs at 4.0 mmol/l. The graph below shows the increase in lactate at different speeds and heart rate.

Screen Shot 2016-07-02 at 6.49.02 PM

Test results – My aerobic threshold occurs at 2.00 mmol/l at 8.6 kph & 148 bpm. My Lactate (anaerobic) threshold was at 4.00 mmol/l at 12.2 kph & 175 bpm.

Once the test is complete, the data captured can be used to create a very specific profile for the individual.


The chart above is the result of the test.  My aerobic threshold occurred at 148 BPM, which pinpoints the top of my Zone 1.  My lactate threshold occurred at 175 BPM, which plots where my zone 3 is, and lastly, my maximum heart rate indicates the top of my zone 5.  Using this information, and plotting it against the speeds I ran at, a set of pace groups is created for each zone.

By training correctly with this information, you can make incredible developments in your speed and running efficiency. Knowing exactly where my thresholds are, allows me to make smart choices when training by heart rate or pace.



I have seen over the last year of performing these tests that my running performance has significantly improved. The results enable you to make better use of your time with faster results. I would highly recommend having the test done if you are keen to improve or train more efficiently.

Peak Performance in Vancouver run these tests and would be happy to help guide you further.



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