There are training sessions you do for the results. And there are training sessions you do because they are simply enjoyable. Fartlek is the rare training that is both.
The word "fartlek" sounds odd, but the concept is as simple as it is effective. No stopwatch, no track, no schedule. Just running and accelerating whenever you feel like it.
Why fartlek works?
Fartlek trains both your aerobic and anaerobic system in one session. During the quiet parts you build up aerobic endurance. During the accelerations you challenge your lactate threshold and VO2max. And because you choose the intensity yourself, you subconsciously adapt the training to how you feel that day.
Additional advantage: fartlek teaches your body to deal with changes in pace: exactly what happens during competitions and terrain changes. A hill in the race, a competitor who accelerates, an opponent you have to overtake. Those who train fartlek respond more smoothly.
And there's something else that has scientific evidence but is rarely spoken about: fartlek keeps you motivated. Fixed interval schedules are mind-numbing if you do the same thing every week. Fartlek is different every time.
Who is fartlek suitable for?
For everyone. That's not a cliché. It literally is. Beginners use it to get used to pace changes without the pressure of precision interval training. Advanced runners use it as a change, as recovery training with occasional acceleration, or as a mental reset after a heavy training period.
Fartlek is also an ideal bridge between easy endurance running and structured intervals. If you're ready to train more intensively but aren't sure if you're ready yet, start with fartlek.
How do you do a fartlek?
There are two approaches: free and structured.
Free fartlek (the classic variant)
Choose a route of 30-60 minutes. Walk slowly for the first 10 minutes as a warm-up. Then you accelerate whenever you want: to a landmark, for 30 seconds, for a minute... Whatever. Recover quietly. Speed up again. The pace of the accelerations varies: sometimes a brisk trot, sometimes almost a sprint. All is well. Finish the last 10 minutes quietly.
Structured fartlek (for more control)
Do you want a little more structure without the rigidity of interval? Use time blocks. For example: every 5 minutes you speed up 1 minute. Or: alternately 2 minutes at a fast pace and 3 minutes easy. This gives you a workout that is more interval-like, but still feels flexible.
Mona fartlek (for advanced players)
A popular variant invented by Australian Olympian Chris Wardlaw. Construction:
- 2 x 90 seconds hard, 90 seconds recovery
- 4 x 60 seconds hard, 60 seconds recovery
- 4 x 30 seconds hard, 30 seconds recovery
- 4 x 15 seconds hard, 15 seconds recovery
Total session: ±20-25 minutes plus warm-up and cool down. Progressive in intensity, achievable in duration.
Sample schedule for beginners
- 10 minutes of walking quietly (zone 2)
- 20-25 min fartlek: accelerate to a landmark each time, then recover at a leisurely jog
- Aim for 6-8 accelerations of 30-60 seconds
- Walk quietly for 10 minutes
Sample schedule for advanced students
- 10 min walk in
- 30 min fartlek: 10-12 speeds ranging from 45 seconds to 2 minutes
- Vary the pace of the gears: alternate between 10km pace and faster
- 10 min walk
Fartlek vs interval training: when do you choose which?
| Fartlek | Interval training | |
|---|---|---|
| Structure | Free, by feeling | Captured |
| Recovery time | You don't stop | Active recovery |
| Need a job? | No | Helpful but not mandatory |
| Mental strain | Low | High |
| Measurability | Low | High |
| Best for | Variety, fun, bridge to interval | Targeted speed improvement |
If you work on your 5km time in a targeted manner, structured interval training is more effective. But if you need a mental break, want to make your training more fun, or just want a good quality workout without too much thinking: choose fartlek.
Common mistakes
Treat each acceleration as a sprint
Fartlek is a game, not a battle. The accelerations do not have to be maximum. Vary the intensity.
Take too little recovery
Because you never stop, there is a tendency to make the quiet parts too short. Make sure you start the next gear really rested. Too high a basic intensity makes fartlek a slow interval training without the benefits of real rest.
Building up too far too quickly
Start with short accelerations. As you get used to the pace, you can increase the duration and intensity.
Frequently asked questions
How many times can I train fartlek per week?
Can I do fartlek without a heart rate monitor?
Is fartlek suitable as preparation for a competition?
Related workouts: Interval training · Zone 2 training · Hill sprints · Training zones
Bart Vandenbussche is passionate about sport and never shies away from a sporting challenge. He has run several marathons (including sub-3h), is an Iron+Ultra Viking, and currently has the Hyrox bug.
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