Training for endurance running performance and the 80/20 rule


For anyone new to running, any type or intensity of running will be effective at improving both fitness and running performance. But, those who are more experienced at running or interested in improving performance as efficiently as possible should follow a few simple, evidence based rules.


80/20 Rule

The 80/20 rule has been used by elite athletes and olympians for years, but was recently coined in research by Professor Stephen Seiler who is a world renowned Exercise Physiologist and Researcher from Norway. This rule states that aerobic training should broadly follow a 80/20 split, where 80% is low intensity training and 20% is high intensity training. This lower intensity can be measured with heart rate or pace, but easily measured with the talk test; if you are able to hold a conversation during your run then you’re running at the right pace. The higher intensity needs to be high for this 20% of your training and you should be breathless and unable to talk. This type of training has previously been called polarised training and used by rowers, cyclists, cross country skiers and runners from 5k to ultra marathons. It has also been shown in Professor Seiler’s research where a 80/20 split improved 10km time trial results by 5% compared to 3.5% improvement in a 50/50 split.


The 80/20 rule is a board recommendation and allows for variation. For example, if someone is running 4 times a week, around one of these runs should be a high intensity run and the others slow, easy running. If all these runs are the same distance, this would create a 75/25 split but still fits within the general scope of the rule. 


Now, this may sound counter intuitive, most would think that to run faster you need to run fast! But for endurance performance, longer events usually aren’t limited by how fast you can run, but how long you can last or ‘endure’ at a moderate intensity. The lower intensity also allows for less accumulation of fatigue and therefore higher overall training volumes to be achieved.


Fitting these runs into the week is often a difficult task for recreational runners. As a general rule of thumb, the week should be split into one fast run, one long run and the rest of the week filled in with as much low intensity running as possible. The long run is most commonly completed on the weekend where you would have the most amount of time and the high intensity run during the middle of the week to allow for the most amount of time to recover in between. 

Strength training 1-2x/ week can also be beneficial as it has been shown to both reduce injury risk and increase running economy. 


A great resource is the Mcmillan Running Calculator which you can input your most recent running results and the calculator will produce guide paces for each of your run types. Just follow the link below:


For any additional information on training, book in to see some of our resident runners and Exercise Physiologist below:

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