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  • Writer's pictureTom

The Easy Interval Method - a revolutionary approach to running training

Updated: Sep 8, 2023

I first came across the Easy Interval Method, or EIM as it's also known, several years ago. I dismissed it at the time as a gimmick or for Masters runners who can't handle the rough and tumble of good old fashioned hard workouts. There wasn't much information about it online to convince me otherwise. At the time I was pretty deep into the '80/20' or 'polarised' school of running training, clocking up the vast majority of my miles at an easy pace while making sure that no more than 20% of my volume (in fact on average it would rarely be more than 15%) was done at faster paces.

As with most training methods, applied consistently it brought about improvement and I felt like I'd found my running philosophy for life. However as time went on I noticed that I was getting a diminishing return from my mileage, and that only by cranking it up could I get more gains. And if I wanted to go faster, then for every 1 mile that I wanted to add to a workout, I would need to add 5 easy miles. Before I knew it I was piling up 70+ miles a week, while also knocking out hard sessions, wanting to make them count. I felt pretty knackered as a result. It always required a lot of tapering down to be race ready. Turning 40, with a new baby in the house, I couldn't remain on this slippery slope of more and more miles. So I picked up a copy of the Easy Interval Method by retired Dutch professional runner Klaas Lok and decided to find out what it's all about.

The first thing to say is that unlike the vast majority of books on running training, it's rare to find one written by an actual former elite runner. Most books as well as articles you read are more likely to be written by journalists covering running and distilling what they believe to be true. However in my experience, this has a tendency to either simplify, cherry pick, or fundamentally misinterpret or draw the wrong lessons from how they believe elites train. I liked the fact that Klaas Lok had taken the time to not only share his training philosophy, but provide a blueprint for what is in fact a complete training system.

The enemy, in his view, is what he calls 'steady-state running', which I interpret to essentially mean the easy miles which might make up the '80' of 80/20. These, he believes, while obviously needed to help support the development of an aerobic base, are over-relied upon by amateur runners, who as a result of this over-reliance do not develop the smooth and efficient running style that maximises your fitness and enables you to run faster - the style of running that you see when you watch elites.

And this is the crux of the issue for Lok. While lots of training guidance will talk about 'engines' and 'aerobic tanks' and whatnot, running cannot be reduced to a mere question of fitness. Running is a biomechanical movement, which, like all movements, needs to be practiced in order to master it. 'Steady-state running', performed by amateurs, is not normally run at the speed where you can glide across the ground, taking advantage of what Lok calls your body's 'reactivity' (interestingly I've heard this described by other writers, some refer to 'suppleness' while others call it 'elasticity'). When we race, we run at speeds which require the advanced mastery and manipulation of this reactivity. Yet, for the runner who follows for example an 80/20 model, the overwhelming majority of their time spent running is not practicing the development of this. For low mileage runners, this might mean that they only do one session a week at faster paces. How, then, to get more quality miles into your training week without ending up on the physio table? The answer is easy intervals.

Of course, easy is a relative term. Most people who have experienced intervals in a running club session will know that they are typically not easy. Spurred on by the presence of others, a weekly track session is often harder than a race, with no upper limit placed on the performance of 400s, 800s, 1200s etc. I am often on the floor by the end of a session, and completely beaten up for the days that follow. It's therefore surprising on first glance to see an EIM schedule look something like this:

  • Monday: 400 x 10

  • Tuesday: 1000 x 6

  • Wednesday: 200 x 15

  • Thursday: 1000 x 6

  • Friday: rest

  • Saturday: 400 x 10 (extra easy)

  • Sunday: Long run or race

The key is to stick to the pace range which Lok provides the reader via a table, whereby you take your current 10k time and are then given a time range for 200, 400, 1000 and 2000m intervals. For example, I am currently in 34 minute 10k fitness, so my 400m EIM pace range is between 1 minute 18 seconds and 1 minute 24 seconds. The intervals I perform for that session should all aim to be in that range, not a problem if a little slower but certainly not any faster. Now, if I go to a club session and we're doing 400s, I will likely be drawn into trying to do them in around 1 minute 15 seconds. Oh, and there'll be 20 of them. So 10 intervals at 1:24 is certainly a lighter workout.

And this, it seems, is the magic of the system. Run with warm ups, generous recovery times between intervals (oh yeah, those club sessions are likely done with 60-90 seconds rest between intervals) typically the same distance as the effort, and with walk breaks encouraged, these sessions leave you feeling pretty great. You are taking your exertion up to a point where the likelihood of overload or accumulated fatigue is reduced, meaning that you can recover quickly and do another interval session the following day (or even later the same day, as prescribed in his more advanced plans). With the ability now to profit from repetition, it's the accumulation of many intervals over many days and weeks where improvement takes place.

If this notion of controlled effort sounds familiar, it may be that you've come across the Norwegian model, aka how Jakob Ingebrigtsen trains. On closer inspection I don't see much difference between the two models. I think that EIM is better suited to amateurs as there's more opportunity with it to develop good running form, something that Jakob certainly doesn't need extensive practice in. The extra precision provided by the lactate meter, meaning that workouts can be pushed right up to the limit before fatigue accumulates, indicates to me that the Norwegian model is more likely to push the elite athlete.

Not going to the wall in a workout feels a bit strange at first, but it's not all easy. That's because, much to my delight, Lok places a lot of importance on racing regularly. It's here, rather than in the workouts, where you get the opportunity to push the envelope and showcase your fitness. Under 80/20 it felt like I rarely wanted to race or had time to, trapped in high mileage and always recovering from hard workouts. With EIM, you are primed to be race-ready and it's not uncommon in the plans that Lok provides to find races scheduled on a fortnightly basis.

Overall, I love this approach and it's changed how I think about running, not just as a challenge to become as fit as I can be, but as a skill to master. If we must use car analogies, then it's not just about building the biggest engine. It's about having the wheels to move it along. The training I have found to be fun and invigorating. Perhaps the one downside is the incompatibility with group running. It is probably better suited to runners who do the majority of their training alone (although for advanced runners Lok does periodically recommend the type of session that you might find at a club workout, just perhaps try not to get over competitive). I would never urge someone to stop running in a group in order to follow the EIM system, and maybe it's possible to persuade others to adopt this approach. Perhaps that is the true calling here, to spread the word, because in my opinion this is a drastically under-appreciated approach to training that flips conventional wisdom on its head, and to me simply makes a lot more sense for the amateur runner. And I say amateur, but really I mean anyone who takes running seriously. If it's good enough for someone who was running 28:24 for 10k (what's that with a pair of Dragonflies?), then it's probably good enough for you too.

As far as my own running goes, I'm only around 6 months into following EIM, but in that time I've achieved personal bests at 5k (16:10), 10k (34:45) and the marathon (2:49:29) - yep, it works for marathoners too. Out of interest, I mapped my EIM training into one of my old 80/20 spreadsheets to see how this training measured up against my old metric, and I found that I was running around 55-60% of my miles at easy pace, with 40-45% intervals. So, around 2-3 times more quality running, all on lower mileage (my recent marathon block averaged 57 miles a week), delivering PBs and feeling great while doing it. If this isn't the revolution then what is?

One of the aims of this post is to try and summarise what it is, and hopefully encourage others to try it out, so if you need something to help make the argument then please do share it!

I've only scratched the surface here. Lok goes into much more detail in the book and provides the reader with training plans based on their preferred distance from 800m up to the marathon, and their availability from 3 to 7 days a week. I recommend everyone visit where you can purchase the book. Once purchased, you are given entry to a lively Facebook group moderated by Klaas Lok himself.

Otherwise if you are interested in finding out more about EIM and would like to incorporate it into your running, contact me and we can discuss it in more detail. If I don't reply right away, it's because I'm out doing my 1000s.

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1 Comment

Klaas Lok
Klaas Lok
Sep 07, 2023

Hi Tom, Great article, very well written, love it! For anyone who is interested in my book: you can download a preview here:

On the first page links where you can buy the book: Amazon (hard copy & eBook) and Apple (eBook). Thanks! Best wishes,

Klaas Lok (author)

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