What it is
Fartlek is Swedish for "speed play", and it means exactly that: an otherwise easy run with faster surges scattered through it, judged by feel rather than by a stopwatch.
You run easy, decide you'd like to go hard for a bit, go hard until you'd rather not, then settle back to easy until you've recovered. Repeat. There is no track, no measured distance, and no lap splits to hit.
The method came out of Swedish distance coaching in the 1930s as a deliberate alternative to rigid track work, and it has survived because it turns out you can get most of the benefit of a structured session without any of the structure.
Why it works
Physiologically, a fartlek session is an interval workout in loose clothing. The surges push you well above threshold; the easy running between lets you recover enough to do it again. Your body responds to the intensity, not to whether you measured it.
What it removes is the psychological weight. A track session has a target you can fail; a fartlek has no target at all, so there's nothing to fail. For a lot of runners that difference is the reason the session actually gets done.
It also teaches something structured work can't: reading your own effort. Because nothing tells you when to start or stop a surge, you have to develop a feel for how hard you can go and how long recovery takes — which is precisely the skill that racing requires.
That combination makes it the friendliest first step into fast running. If intervals sound intimidating, start here.
How to pace it
Two efforts, alternating:
- The surges. 7–8 out of 10. Hard enough that you wouldn't want to talk, controlled enough that you could keep going a bit longer than you do.
- Between surges. 3 out of 10 — genuinely easy. This is the part people skip, and skipping it turns a fartlek into a long, unfocused hard run.
Don't measure. The whole point is that you're judging both by feel.
A sample session
40 minutes easy with 8 × 1 minute surges.
Better still, drop the clock entirely and use the route: surge from one lamp post to the third one along, then run easy until you feel ready. Pick up the pace on every uphill and float the downhills. Race a bus stop.
The landmark version is more fun and, oddly, tends to produce better-judged efforts than the timed one — you stop watching the seconds tick down and start paying attention to how you feel.
Where it fits in your week
Once a week, as your quality session, in place of intervals or a tempo run — not in addition to one.
It's especially useful in a base phase, when you want to keep some speed in your legs without committing to formal workouts, and during a break from structured training when you still want one run a week to have some bite.
Keep the day after easy, the same as any workout.
Common mistakes
- Turning every surge into a sprint. Go too hard on the first three and the last three become a shuffle. The set should be repeatable end to end.
- Never actually returning to easy. If the "recovery" is base pace, you've run a 40-minute moderately-hard run, which is the least productive thing in distance training.
- Over-structuring it. If you find yourself planning exact surge durations and recoveries the night before, you've reinvented interval training. Run a proper interval session instead, and let the fartlek stay loose.
Track it in Kamee
Track it with GPS, then ignore your watch completely while you run — this is the one session where live pace works against you. The splits afterwards are the interesting part: you'll see the surges as a sawtooth, and you'll usually find your surges got shorter as the run went on, which is a useful thing to know about how you judge effort.