The fartlek is one of the most enjoyable workouts to include in a runner’s training programme. Its name comes from Swedish and means “speed game”: an expression that perfectly captures the spirit of this training method, which is based on alternating different running paces without necessarily following a rigid structure.

Unlike traditional interval training, fartlek leaves room for spontaneity. You speed up, slow down and change pace according to how you feel or the different stimuli you encounter along the way.

The origins of fartlek

The method originated in Sweden in the 1930s, thanks to coach Gösta Holmér, who developed it to improve the training of Swedish distance runners. The idea was to combine speed and endurance through a less rigid approach than traditional interval training.

The concept was simple: run on varied terrain, alternating faster sections with easier ones and making use of the natural features of the route. A hill, a tree, a stretch of trail or an easily recognisable landmark could become a reference point for deciding when to speed up and when to recover. There were no specific distances or times to stick to: it was a workout that allowed runners to manage their pace more freely.

How does fartlek work?

In its original form, fartlek is essentially a game of speed. You can decide to accelerate until the next streetlight, run faster up a hill, pick up the pace to reach a tree and then slow down to recover. Little structure, plenty of spontaneity: there’s no need to keep checking your watch or decide in advance how long each change of pace should last. You simply alternate faster and slower sections according to how you feel, the terrain and your level of fatigue.

Nowadays, you’ll often come across workouts labelled as fartlek that involve, for example, one minute of fast running followed by two minutes of easy running, repeated a set number of times. These are certainly valid workouts, but in my opinion, they represent a more structured version that comes much closer to interval training. Personally, when I think of fartlek, I prefer to stick to its original spirit: less watching the clock, fewer rigid structures and more freedom to play with your pace.

That’s exactly what makes it different from other quality sessions: it’s a way to add some variety to an otherwise more straightforward run, without having to push yourself as hard as you would during a block of intervals.

What is fartlek training good for?

Alternating different running paces allows you to work on several aspects of your training:

• Speed: incorporating accelerations helps you become more comfortable running at faster paces.

• Endurance: alternating harder efforts with active recovery allows you to keep training even as fatigue builds up.

• Effort management: learning to change pace and recover while running is also useful during races.

• Adaptability: running on different types of terrain and gradients helps you handle conditions that differ from those of a flat, regular course.

• Motivation: varying your effort in response to external stimuli, almost like a game, can make a workout feel less demanding mentally.

In short, fartlek makes training less monotonous and allows you to introduce some quality work without having to follow a precise, second-by-second training plan.

When should you include fartlek in your training?

Fartlek can be useful for runners of different levels, provided they already have a basic running foundation and can comfortably handle a workout involving changes in intensity. I’d particularly recommend it when you want to introduce some speed without tackling a highly structured interval session, or simply when you feel like doing something different from your usual steady-paced runs.

It’s also a great way to train on less predictable routes, such as parks, trails and roads with hills and descents, where following precise intervals can be impractical.

Of course, not every acceleration needs to be an all-out effort. You can gradually increase your pace, listen to your body and allow enough time for recovery. As with any demanding workout, it’s best to start with an adequate warm-up. Personally, I avoid introducing extremely fast accelerations during a fartlek session, apart from perhaps a few very short strides.

My advice: rediscover the joy of running

The beauty of fartlek is that it shouldn’t become yet another workout where you spend every second checking your GPS watch. You can start with an easy run, pick a landmark ahead of you and accelerate until you reach it. Then slow down, recover and pick up the pace again when you feel ready. There’s no need for every acceleration to be identical to the previous one (quite the opposite!) and it doesn’t matter if one lasts thirty seconds and the next one a minute and a half.

Fartlek is an opportunity to break away from routines, listen to your body and have fun with speed. Sometimes, training well doesn’t mean planning every single detail or constantly checking your GPS watch.