How to run your fastest marathon time with the 80/20 training plan

As a physiotherapist and a 2.31 marathon PB runner, I have learnt the hard way that the three laws of marathon running are: #1 don’t get injured. #2 don’t get injured. #3 don’t get injured. The 80/20 training plan allows you to run more mileage, train more consistently and have a greater chance of hitting a marathon PB.
Picture of Jimmy Goulis

Jimmy Goulis


80/20 running is also known as polarised training. It was developed by Dr Stephen Seiler, one of the world’s leading minds in sports science. He’s worked with some of the best athletes across the globe, in a variety of sports including running, skiing, rowing and cycling.

Seiler’s research has shown that this 80/20 split is the most effective way to train for long distance running events, from 5km right up to marathon distances.

His research shows that to improve performance, training needs to be sustainable. This means being able to repeat training week after week. 

There are 365 days in a year, if you train five days a week by 52 weeks, that’s 260 sessions a year. Don’t ruin a whole year of training with a single heroic session that makes you injured.

By following the 80/20 method, you can train for long periods of time without getting injured, fatigued, or physically and mentally burnt out.

As an avid runner and Strava user, I have noticed that athletes generally fall into three categories:

  • The yo-yo
  • The crash-and-burn
  • The metronome

The yo-yo trainer

The yo-yo trainer tends to get inspired for short periods of time, they have a stop-start style of training, never fully realising their potential.


The crash-and-burn trainer

The crash-and-burn-style runner does a lot of mileage, a lot of high intensity, eventually gets injured and burnt out and is forced to stop training altogether.


The metronome trainer

The metronome runner is that person who does all the right things. They train consistently, do not overdo hard sessions and seem able to back up, week in, week out.
The metronome style of training fits into the 80/20 methodology because it’s sustainable and people can maintain the training for long periods of time. If you’d like to develop the consistency of the metronome runner, following the principles of 80/20 running will help you get there.

Steps to implementing 80/20 running



Calculate your maximum heart rate

One of the most important steps to implement 80/20 running is to know your maximum heart rate. Traditionally, this has been calculated using the formula: 220 minus your age. 

So, if you were a 40-year-old runner, your maximum heart rate would be 200 – 40 = 180 beats per minute. 

However this formula is based on population norms and can vary significantly for individuals. This is why it is important to calculate your true maximum heart rate using a heart rate monitor and an exercise test. Chest-strap heart rate monitors are more accurate than a wrist-based heart rate monitor. The latter can be used if you don’t have a chest strap but understand that it might not be as accurate.

Examples of exercise tests include hill sessions, a 5K race or fast track session.  

Here’s how you do the hill test:

  1. Find a steep hill that would take about 2 minutes to ascend.
  2. Warm up for 10 minutes with some gentle running.
  3. Run up the hill for your first two efforts at moderate intensity.
  4. The third effort should be at all-out, maximum effort.
  5. Remember, you will be jogging down the hill as soon as you’ve completed each hill rep.

This is a test to discover your true maximum heart rate and this should be reached on that final hill repetition. There are of course more expensive lab tests that can be done, these can measure everything from your maximum heart rate, VO2 max to lactate threshold. For the average person, however, a field-based test is a good starting point. Remember, always consult your doctor or physician before undertaking any hard physical exercise.


Intensity: Find your right training zone

Now that you have your maximum heart rate you have the crucial piece of information to help calculate your training zone range. There are five different heart rate training zone ranges and these are illustrated below.


Percentage of heart rate max

Borg scale (intensity)



Very light













Whilst this may seem confusing to the average runner, the 80/20 running method allows us to simplify this to 2 zones, easy (green zone) or hard (red zone). The key is to avoid the moderate intensity grey zone. 

An easy run should be performed at about 60 to 70 per cent of your maximum heart rate. For example, if your maximum heart rate is 180 beats per minute, an easy run would be between 108 to 126 bpm.

If maths wasn’t your strong point at school, head over to the Polar website. They have a great heart rate zone calculator.
It takes a lot of discipline to slow down on these easy run days. Strategies that can be used to ensure you’re in the right range include monitoring your heart rate, the talk test, which means being able to comfortably hold a conversation while running, or using the Borg Rating of Perceived Exertion. This is a self-assessment tool that helps people rate their perceived exertion on a scale of 1 to 10.

This is a self-assessment tool that helps people rate their perceived exertion on a scale of 1 to 10.

1 /

Very light activity

Hardly any exertion

2-3 /

Light activity

Feels like you could maintain this level for hours. Can easily breathe and hold a conversation

4-6 /

Moderate activity

Moderate activity Breathing heavily but can hold a coversation

7-8 /

Vigorous activity

You're short of breathe and starting to feel uncomfortable

9 /

Maximum effort activity

Almost impossible to keep going. Completely out of breath and can't talk

10 /

Very difficult activity

Very difficult activity Very hard to maintain exercise intensity. Can barely breathe and can only speak a few words

The benefits of running in the easy training zone

  • Improved endurance and aerobic capacity.
  • You get better at burning fat.
  • You develop greater capillary density so your muscles have better oxygen carrying capacity.
  • You also improve your cardiovascular system by increasing its efficiency.
  • Allows adaptation of tendons, joints and bone.
  • Improved running efficiency.
  • Increases in the quantity and size of mitochondria, which means more energy available for use.
  • Reduced risk of injury.
  • Reduced risk of burnout.
This is also about celebrating the true joy of running! You’re slowing down, you’re smelling the roses (or the gum trees), you’re taking in the scenery, there’s no pressure to run fast, there’s no competition. These runs are about embracing the freedom of running and it’s the reason we all started in the first place. In a lot of ways, 80/20 get us right back to our roots. Sometimes it’s easier to do your slow runs solo or with someone at your level and following the same training plan.

Here are some of the common running mistakes:

  • Running with faster runners on your easy day.
  • Letting your ego get in the way of your long-term plan.
  • Getting stuck in a moderate intensity rut for all of your runs.
  • Believing there’s a magic bullet to suddenly running faster.
  • Not understanding that a lot of the training is not always glamorous, it can sometimes be a daily grind. It’s normal to not always feel motivated and inspired.
  • Not understanding that all good athletic performance needs to be built on solid foundations… which is essentially lot of slow running


Frequency: Work out how many days a week you can commit to training

Once you’ve established the right training zone or intensity, the next decision you need to make is how many days a week you can commit to training. Each runner needs to work out their optimal total weekly training time or training volumes. Make sure that you choose a frequency that is realistic and sustainable. Take into account all of the competing demands in your life, for example, work, family and other commitments. It is better to err on the side of caution and create a plan that you can commit to over the long term rather than stopping and starting.



Duration: How long should each session be?

Once you’ve established intensity and frequency, the next question should relate to how long each session will be. The distance that you are training for will help to determine this to a large extent. For example, a 5K runner versus a marathon runner will clearly need a very different duration. Also think about your starting point, which is the normal distance you currently run, and start to make it a bit longer week after week. But never increase your duration more that 10 to 15 per cent per week.

This might mean that a 30 min run becomes a 35-minute run, then a 40-minute run and so on.

  • 3 easy runs per week of 30-40 minutes duration each.
  • One long, easy run (duration depends on the distance of the race you are training for).
  • One hard session (discussed later in this article).

How long should I run when training for a marathon?

The most important run of the week for marathon training is the long run. This should be at an easy pace and gradually built up week after week. Beginners should allow at least five to six months to build up to a marathon race. More experienced runners can often build up over 12 to 16 weeks. It’s recommended that you build your long run up to 30-35km. Most coaches agree that the risk of injury and burnout outweighs the benefits from running any further in training. The marathon is a war of attrition; running for 42.2 kilometres requires a lot of conditioning of the heart, tendons, muscles, bones and brain. All need to be trained to cover that distance

The other 20 per cent: What sort of hard training should I be doing?

We’ve covered the essentials of slow running. That, however, is not the entire story. To really improve our running performance, hard sessions are a must.

The benefits of hard running include:

  • Increased speed.
  • Improved power output.
  • Enhanced muscle strength.
  • Improved ability to use carbohydrates for energy.
  • Improved ability to withstand higher levels of lactic acid in your blood for longer.
  • Improved cardiovascular fitness.

What type of hard sessions can I do?

The research shows that the best type of hard sessions are interval sessions, tempo runs, threshold runs and Fartlek training.

Interval sessions

With interval sessions, research shows that anything from 3- to 8-minute efforts are optimal.

These are usually considered zone 4 sessions, they are hard at 80 to 90 per cent of heart rate max.

With interval sessions, the principle is to run hard for a defined time or distance, with a rest break in between. Some people prefer to run intervals based on time, others prefer distance. Research shows that it doesn’t really matter which one you choose, as long as you accumulate minutes in these hard zones.

Some examples include:

  • 3 x 8-minute efforts with 2-minute recovery in between.
  • 6 x 1 km efforts with 1-minute recovery in between.
  • Yasso 800s: 8 x 800 m with 2 min recovery in between.

A lot of runners are unsure about how to approach the recovery period during hard session. Research tells us that you can have a standing rest, a walk rest or a jog rest. Anywhere from 1 to 2 minutes is appropriate. The term float confuses a lot of runners, it just means a faster jog recovery and should be used by more experienced runners.

Tempo runs (threshold runs)

A tempo run, (also known as a threshold run) is a sustained hard effort that builds up your body’s ability to run faster for longer periods of time.

They are generally zone 3 moderate effort at 70 to 80 per cent of heart rate max.

Typically, you would find a pace that you can maintain for at least 20 minutes or more. The benefit of tempo running is that you build your lactate threshold. In other words, as you practice running at fast paces you get better at clearing lactate from your muscles. By practising at this pace, your body also gets more efficient at holding this pace for longer

Fartlek training

What is fartlek training? Fartlek training means ‘speed play’ in Swedish. It involves continuous running where periods of faster running are mixed with periods of easy to moderate running (not complete rest, as occurs with interval training).

The classic Mona fartlek, developed by Steve Monaghetti, is a good example of a fartlek session:

  • 2 x 90 seconds hard, 90 seconds easy to moderate (float).
  • 4 x 60 seconds hard, 60 seconds easy to moderate (float).
  • 4 x 30seconds hard, 30 seconds easy to moderate (float).
  • 6 x 15 seconds hard, 15 seconds easy to moderate (float).

Beginners should start with an easy recovery and build towards a faster paced, moderate recovery.

It’s important to remember that hard training should only make up 20 per cent of your total training. These sessions should only be attempted after you have established a baseline of slow running, are feeling injury free and feel ready to take on more challenging workouts.

Doing these sessions in a group can help you get through because they are quite challenging to be done on your own. This is where you want your competitive spirit to push you to greater levels of fitness.



Summary: What is the 80/20 rule for exercise?

It may seem counterintuitive that running slow will help to make you faster, but it’s backed by science, is more sustainable and enjoyable and more likely to help you achieve your goals.

In a nutshell:

  • Find your maximum heart rate.
  • Calculate your training zone.
  • Decide on how many session per week.
  • Decide how long these sessions should be.
  • Do slow sessions easy.
  • Do hard sessions hard.
  • Be patient.
  • Stick to your plan.
  • Enjoy running!

If you’re interested in learning more straight away, visit Stephen Seiler’s youtube channel or his Twitter feed.

If you’d like help with your training program or your injuries, Pollinate Health is here to assist. We offer running assessments, running programs, injury screening and management, targeted strength training programs and more. We’re also well equipped to consult via telehealth, so interstate and international clients are welcome.

Remember, before you make any major changes to your training program, especially adding intense activity, make sure you see your GP or specialist.

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