Avid users of social media may well just have spotted that the great Kenyan double Olympic 1500m champion, Faith Kipyegon, has been at it! In fact its been a staple part of the training diet of athletes for almost a century! What its it? The session we are alluding to is known as the ’fartlek’.

Energy systems

This famous mode of training session which fantastically brings into play not one, not two but all three energy systems! These energy systems are the holy trinity of our quasi-religious ritualistic commitment to training. They are of course the aerobic (with oxygen) system, the lactate system (which we associate with speed endurance) and the (‘stop-start’) system.   


Fartlek is a derivation of the Swedish notion of ‘speed play’, which was developed in the late 1930s by the legendary coach,Gösta Holmér. Now the original conceptualisation of fartlek was that it should be fluid and unstructured rather than characterised by rigidity and overt structure. If he were alive today, the founder father of the fartlek would smile if he saw you embrace the core ethos of running steadily and occasionally putting a range of differentially paced and distanced ‘surges’ into your run. 

How To Effect

So in what way was the fartlek intended to be unstructured? Well you may for instance hit the roads and decide to surge to that pub high on the hill half a mile or so away and in the 3 minutes or so that it takes you to get there you would be running at an aerobically dominant pace. After walking for 50 yards or so you may break back into a jog for a minute or so before resuming steady running. After several more minutes you may intuitively decide to surge once more to that bus shelter 400 yards or so away on the left-hand side of the road. In doing so you may be bringing your lactate system into play. After repeating the washing machine-like cycle of walking, jogging and steady running once more you may decide to sprint to the sign depicting the local post office which is just 60 metres or so ahead of you. In so doing you would be bringing your alactic energy system into play. 

It’s unstructured because you haven’t pre-planned any of this, you are in essence making it up as you go along. A typical 5 mile or 8km (ish) fartlek might see you taking a mile or so to warm up and cool down but in the middle segment of 3 miles or 5km you might be able to surge typically 5 or 6 times There’s no splits to pre-programme into your watch or targets for you to hit! You are inevitably reliant on ‘feel’ which Lewis and Matt spoke about in episode 13 of the New Levels podcast and this inevitably causes some athletes a level of cognitive disorientation.


Think back…have you ever test driven a car before its purchase? Do you remember being handed to keys by the showroom salesperson who escorts you to your vehicle whilst proceeding to sit alongside you in the passenger seat to make sure you don’t actually steal the vehicle?! When you test drive a new car you simply can’t blast off in 5th gear with your foot firmly pressed down on the accelerator with smoke bellowing out of the exhaust or you will upset the showroom salesperson! So you gently take the car through all five years. Up into second gear as you turn left out of the garage forecourt, then into third as you navigate an industrial estate and then into fourth and fifth gears as you are allowed a quick spin on a stretch of the nearby motorway. A fartlek sees you metaphorically ‘moving through the gears’ without thrashing the proverbial engine. 

If that analogy doesn’t work for you, close your eyes and visualise the last time you were out in the local park and you saw a small puppy being let off its lead by their owner. That excited puppy will move about multi-directionally before suddenly stopping to pant and then resuming its activity at a frenzied pace. That young puppy is in effect undertaking its own variant of the fartlek. 

Where to Effect

As well as road, the fartlek can also be effected on the trails or on grassy parkland and its unstructured and improvised nature can be retained by swapping landmarks such as pubs and bus shelters with things like trees and benches. Less commonly the fartlek can and is effected on a track but inevitably this is when its original conception of being playful and intuitive begins to be superseded by its 21st century variant which is more formalised, structured and split based. There is a fine line between this latter conceptualisation of the fartlek and what would be termed as aerobic intervals. At this point some athletes make the mistake of focussing on the ‘speed’ but forgetting the ‘play’ side of the real spirit of the fartlek as envisaged by the aforementioned Holmér. 


We have alluded to the key physiological benefit of the fartlek, namely that it is the one training session which if effected in the right spirit, ticks the box of challenging all three energy systems. There are psychological benefits too in that many athletes report feeling less ‘bored’ than they do on a simple easy run in that time seems to literally ‘fly by’ because they are busy planning their next surge and so on. 

When to Effect

The fartlek is best conceptualised as a ‘bridging’ session. Its not easy enough to constitute a recovery or easy aerobic run but alternatively its not meant to be hard enough to rival an aerobic interval session or repetition-based speed endurance session. Its often best used by athletes (a) returning to formalised training after injury or a deloading period, as a ‘bridge’ back to more formalised modes of sessions. Alternatively (b) it can be used prior to a target race during a taper whereby a structured session may risk over-fatigue but the fartlek can be used as a way of proverbially keeping the ‘legs turning over’.  

This leaves us with the following questions for self-reflection: 

  1. How can fartlek help in terms of the energy system contribution of my training diet?
  2. Where should I best effect a fartlek in terms of surface? 
  3. When should I best effect a fartlek in my periodised training plan?

Matt Long is a Loughborough University based New Levels Coach who has team staffed for his country either as manager or coach on 19 occasions. He has guided two athletes to world titles and two to European titles. An England Athletics tutor, he is a former winner of the British Milers’ Club annual Horwill Award for outstanding coach education research having penned more than 350 coaching articles for a range of national magazines.