Fartlek (Swedish for ‘speed play’) is one of the most common training sessions I use with my athletes. The history of fartlek training dates back over 80 years, when coaches and scientists began to experiment with different methods of improving fitness and adding variety to training. Swedish coach Gösta Holmér developed fartlek training as a way of combining speed and endurance in one session. Here’s what fartlek workouts are, how they’re different from other speed workouts, why you should add them into your training, and how exactly to run them.
What is a fartlek run?
Fartlek is literally, playing around with speeds – essentially, it’s a form of unstructured speedwork. It involves a continuous run in which periods of faster running are mixed with periods of easy- or moderate-paced running (not complete rest, as with interval training).
You can use time as the measurement. For example, running one minute at a faster effort, then three minutes at easy effort. Or you can use distance – run faster for a half a mile, say, then run easy for half a mile.
Fartlek leaves a lot of control to the runner. You can choose to mix a wide range of paces and lengths for your faster efforts, or head out without a detailed structure and just go by how you feel.
How is fartlek different to other speed workouts?
Tempo runs are should feel ‘comfortably hard’ and are run at a consistent pace – typically about 20 to 45 seconds per mile slower than 5K race pace (to figure this out, head to our Runner’s World pace calculator), or the level of effort you feel you could sustain for an hour.
Intervals are short, intense efforts followed by equal or slightly longer recovery time, which might involve slow jogging, or stopping completely. A typical interval workout might be 8 x 400m reps at 5K pace, with recoveries lasting the duration of the rep.
Why should you incorporate fartlek into your training?
They’re a good stepping stone
Fartlek workouts are a great way to introduce faster or more intense running into your routine. Structured fartlek sessions can be particularly useful in the early weeks of a new training plan, to ease runners into the more physically and psychologically demanding sessions they will tackle as they get closer to their goal race.
A taste of the ‘real’
Interval sessions are great, but when the gun goes in a race, you don’t get to stop and rest; you keep moving. Also, races are rarely run at a consistent pace throughout. Fartlek can reflect the real demands of races – you don’t get to fully rest and they train your body to the natural variances in pace that you experience in races.
They put you in control
Having direction, clarity and being guided on a journey can keep you moving forward, but fartlek sessions are great for taking control. You can make your sessions more responsive to how you feel on a given day. On race day, you won’t have a coach telling you when you can push and when to ease back. Fartlek can teach this.
They can be more fun
Fartlek can be a more enjoyable way to train, too. Take a more unstructured approach, run over mixed terrain and undulating routes, and trust yourself to run to perceived effort instead of spending the whole session feeling the pressure of your GPS watch.
Many of you will probably be racing over distances of 5K or longer – these races demand an almost exclusive reliance on your aerobic energy system. By forcing you to keep running during your ‘recovery’, fartlek sessions put a greater focus on your aerobic system and can help teach your body to become good at reusing lactate as a fuel source.
How to incorporate fartlek into your training
There is no 'right' way to run fartleks (that’s the beauty of them!), but there are a few guidelines to help you.
One of the key differences between fartlek training and interval training is that fartlek should be treated as a continuous run. If you find yourself needing to stop or walk between your faster efforts when doing fartlek sessions, you’re probably doing them too hard. Ease off and make your primary focus still being able run on your ‘recovery’.
Trust the feel
Fartleks are best run on feel and not by relying on your GPS or heart rate. Imagine a scale of 0-10. Run your ‘on’ efforts from 7-9/10 and your ‘off’ efforts from 4-6/10.
Give it time
We all like structure and certainty. It can feel uncomfortable to remove that and when you first start to do fartlek sessions, you might get them wrong. You’ll go too hard and need to rest, or include too few or too many efforts. Fartlek training can be a learning process, so stick at it. Keep a training diary and note down what worked and what didn’t, painting a picture and shaping your approach over time.
Use your environment
Make your environment part of the session. For example, go hard to the top of that hill, strong to the next lamppost, float to the gate. Use that environment to structure your sessions. Getting offroad and onto undulating routes can also help you focus on effort, not your GPS.
There are lots of different ways to go about fartlek training. Shorter, faster efforts over 30 and 60 seconds can be mixed with longer periods of easy, steady or threshold running; or you can do longer efforts over five, 10 or even 20 minutes mixed with shorter recoveries. Think about the demands of your race. If it’s a marathon, you might try to include longer, faster efforts closer to your goal race pace. If you are early in your plan or training for shorter races, a good mix of efforts between 30 seconds and four minutes could serve you well.
‘Float’ for a harder session
Consider the recovery sections to be as important as the harder efforts. If you want to make your fartlek sessions harder, try ‘float’ recoveries. These involve running at moderate or steady effort between the faster efforts, rather than an easy jog. Making the recovery harder will create a different stress.
Even though fartlek sessions can be more relaxed in terms of their structure, they are still a hard session in your training week and so they need to be treated with respect. Be sure to give yourself at least one easy day between your harder sessions, and bear in mind that most runners will respond better to two or even three easy days between such sessions.
5 key fartlek workouts
The natural and often most effective way to include fartlek. Pick a route over mixed terrain and include anything from 10-25 harder efforts of between 15 secs and four mins, or use lampposts, hills etc as targets. Run easy or steady during the recoveries.
Great for early in a training plan as a bridge to specific interval sessions: do 10-15 repeats of 30 secs hard, 90 secs steady; building over time to one minute hard, one minute steady, with a good warm-up and cool-down.
A session used by Australian distance runner Steve Moneghetti, this is a versatile 42-min session. If your focus is shorter distances, slow the ‘off’ paces a little and speed up the ‘on’. If racing longer distances, run steady on the ‘off’ sections.
90 secs ‘on’, 90 secs ‘off’ x 2
60 secs ‘on’, 60 secs ‘off’ x 4
30 secs ‘on’, 60 secs ‘off’ x 4
15 secs ‘on’, 15 secs ‘off’ x 4
These sessions are great for 5-10K or cross-country racing: 6/5/4/3/2/1-min efforts, getting faster as you go through, with 90 secs easy or steady running between; or four sets of 3/2/1 mins, with 60-90 secs ‘off’ between the efforts and sets.
Not strictly ‘fartlek’, but useful preparation for the final 10km of a marathon: 4-5 sets of 4km at marathon effort, with 1km steady between each; or 75-90 mins with 60 mins alternating 3 mins slightly slower than marathon pace and 3 mins a little faster than your marathon pace.
Tom Craggs is Road Running Manager for England Athletics
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