David Chalfen reviews ‘Easy Interval Method’ by Klaas Lok (Choir Press)

The nudge to read this came via the recent lively Fast Running pieces on Mihaly Igloi, the ground-breaking Hungarian coach of the 1950s, and the more modern influence of some of these principles by the Dutch author.

As an athlete, Lok has excellent credentials from his peak in the late 1970s to mid 1980s, including a 7:51 3000 (and 2nd place in the European Indoors), 13:36 5000, 28:24 for 10,000, but perhaps the standout on his racing CV was 20th in the World XC in 1980 when the European and USA strength in depth was immense; he was in very close company with some undisputed world class track and road athletes mostly with 10,000 PBs far faster than his.

Interestingly he matched this grinding endurance with superb closing speed, with a swathe of Dutch titles on track, road and Cross – once closing a 5000m track race with a blistering 53.5 which for a man who couldn’t do a one off 200m in under 25 secs is outstanding.

These snippets of data illustrate that a major focus on aerobic conditioning combined with retention of relatively high speeds done without fatigue (achieved by virtue of the session design) meant that fairly light exposure to highly anaerobic stresses proved a tremendously effective balance of stimulus.

Coaching pedigree

His coaching ‘portfolio’ is at least as impressive. Put into the context that the Netherlands has just ¼ of the UK population, is all at sea level and notoriously flat, and that he never had an official Governing Body position so was, arguably, drawing his coachees from a more provincial pool around Utrecht.

Put it another way, if you’re reading this and you’re a woman who wouldn’t be pleased with a 5k PB of 15:22; or (from a separate female coachee) a 10,000m PB of 32.22, or a guy who thinks 62.29 at Half marathon doesn’t pass muster; or a Veteran aged 40 who thinks an 8:15 3000 is nothing to shout about; or a V55 Woman who is ambivalent about the merits of a 79 Half Marathon, maybe you need read no further.

Perhaps the most well-known case study is that of world class 800m runner Bram Som. In headline data, aged 26 he ran a Dutch record (still standing) of 1:43.4 using a ‘classic’ training schedule. Three years later, after injuries so significant that his running was confined to 4 days a week, he spent a season using the EIM and clocked 1:43.5 and made the World Championship final (where just 0.59 behind the gold medal placed him 7th!).

Speed without fatigue

It’s hard to summarise the approach to be both through, accurate and concise at the same time. Simplifying, the bare bones of the EIM takes in one hard session (OR race) per week, usually of a mixed pace nature – fartlek if you will – that keeps in touch with the demands and stimulus needed for the athlete’s target distance(s).

The one detailed example Lok sets out is a truly multi-faceted session and duration (for him as a 28 minute 10k athlete) was 95 to 105 mins all in, with 11 strands not counting warm up and warm down. The other days are nearly all built around the EIM which if it has one specific benefit that ‘traditional’ steady state training may lack is the preservation of ‘reactivity’; the Dutch word is ‘souplesse’ and words like ‘elasticity’ or ‘dynamism of stride’ come close.

Terminology aside, the principle is that it is based on speed (using that word quite flexibly) without heavy aerobic/metabolic fatigue, so the principle of continued recovery between truly intense efforts is not compromised. The staples of EIM are the likes of 10-12 x 200m at around 3k pace with equal distance slow running recovery; and 10 x 400m at between 5k and 10k race pace with equal distance slow running recovery; and 6 to 8 x 1000m at around Half Marathon pace with equal duration easy running as recovery.

All the faster reps have a 10 second walk before starting and after completion, which further lessens the overall intensity. It’s worth mentioning that the book covers all standard distances from 800m to marathon. Perhaps the wider base of case studies is between 3000m and Half Marathon.

It’s worth mentioning that for marathon runners the author absolutely buys into regular (but not every week) long and very long runs, always with some sort of faster shorter periodic surges peppered throughout the run.

For upper echelon runners he extends the 1000m reps to 2000m so this does become quite voluminous; and again at the similar faster end he does throw in some occasional doubles but it’s notable that the second no-interval run on such days is a solid steady pace – so about 5.45 to 6 minute miling for a 29 minute 10k runner.


The particular advantages of the EIM over traditional methods (which he mentions in passing are often based around important and often reductive misunderstandings of relevant details of what Lydiard actually recommended) include the following:-

Too many runners run some combination of too much one paced mileage and do too many intense interval sessions at or around VO2 max, or indeed faster and harder.

Their fast interval sessions eventually, by a combination of being too frequently too hard become destructive rather than productive; and their easy recovery runs are detrimental to their fast twitch capacity and gradually lead to poorer running form and movement, and a poorer running economy (RE) which more than offsets the gains in RE that the mileage itself might be promoting by other physiological adaptations.

That the best athletes in the world by and large follow training schedules which would, in the large majority of runners, lead to the shortfalls mentioned above, is perhaps, Lok suggests, due to their very light bodyweight combined with some great genetic advantages in ‘reactivity’ of stride, keeping them from the detrimental aspects whilst retaining the benefits of the traditional approach.

All abilities

Lok has coached at a very wide range of levels so he writes as credibly about a 28 minute 10k runner as someone taking 65 minutes for the distance, and acknowledges that, for example, Anaerobic Threshold in a newer or much slower runner is not far from their 5k race pace, whereas at the sharpest end it equates more with Half Marathon pace. And indeed he is fully aware of the wide middle ground between these two levels.

A critic could argue that some of the gobbets of advice along the way are based purely on anecdote and experience though he is always candid in pointing out where a suggestion doesn’t have any cast-iron science to back it up or otherwise.

No doubt based on his experience on the coaching scene, Lok has rebuttals for most of the usual reservations about his approach. When criticised on the vast amounts of common ground across his schedules from 1500m to Marathon, he points out that ‘traditional’ coaching also shares this commonality for much of the seasonal cycle; the reason, is that both of the two schools of thought are aware that the 1500m is, simplistically, about a 70 to 75% aerobic event, whereas the marathon is about 99% aerobic; so on that important parameter they are much more similar than they are different (though they are different!).

Having played around with some maths on the weekly volume of Lok’s plans – and find a serious British distance runner who doesn’t have at least some ‘engagement’ on the mileage front – I’d very roughly suggest that if you are typically training between 40 and 60 miles per week, the EIM approach might see you clock up about 15 to 20% less distance (including warm ups and warm downs) and for those piling in more miles, I’m not sure that you can run more than about 70 miles weekly without starting to eat into the basic principles which underpin the EIM approach.

Recommended for athletes and coaches

The English version has been excellently translated by Russ Mullen, himself a fine case study of Klaas’s approach, in between, one assumes, keeping his Dutch very efficiently on the go in Haywards Heath.

I’d heartily recommend the book. It even has photos of runners crawling backwards uphill – apparently a cruel but effective core strengthening drill, and which reminded this reader of Percy Cerruty’s approach in using the natural environment in creative ways.

Plus a whole host of great race photos from Lok’s peak, which reminds you that in the pre African era the Europeans were pretty damned good at distance running. Even if you decide that the approach Is not for you, it will make you think why not and question why do exactly what you do, whether as coach or runner.

David Chalfen is the coach of Serpentine Running Coach and his book has been printed in Czech https://www.kosmas.cz/knihy/196203/trenujeme-na-maraton-a-pulmaraton/ but not yet offered in Dutch…