Fartlek Interval Timer

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00:30
Step 1 / 10

Running order

  1. 1.Effort 00:30–03:00
  2. 2.Float 01:00–03:00
  3. 3.Effort 00:30–03:00
  4. 4.Float 01:00–03:00
  5. 5.Effort 00:30–03:00
  6. 6.Float 01:00–03:00
  7. 7.Effort 00:30–03:00
  8. 8.Float 01:00–03:00
  9. 9.Effort 00:30–03:00
  10. 10.Float 01:00–03:00

10 steps; step lengths vary each run.

Fartlek is Swedish for speed play, and the original idea is unstructured: efforts of varying length at varying intensity, taken as terrain and inclination suggest, with easy running between. The variation is the point rather than an inconvenience — it trains the ability to change pace and recover while still moving, which structured intervals do not.

This timer randomises the effort and float lengths within a range for exactly that reason. A fartlek where you know each effort is ninety seconds is an interval session in disguise, and you will pace it accordingly. Not knowing when the effort ends forces you to run by feel, which is the quality the session exists to develop.

The Mona fartlek

The best-known structured fartlek is the session associated with Australian marathoner Steve Moneghetti: 2 x 90 seconds, 4 x 60 seconds, 4 x 30 seconds and 4 x 15 seconds, each with an equal-length float recovery, totalling twenty minutes[1].

It is structured rather than random, which makes it a different session from a true fartlek — but it is an excellent one, and the descending effort lengths keep the intensity rising as the session progresses.

Float, not stop

The recovery in a fartlek is easy running, not walking and not standing. That is what distinguishes it from an interval session and it is where much of the adaptation comes from — the ability to recover while still working.

Runners who stop during the floats are doing intervals with extra steps. If the floats are impossible to run, the efforts were too hard.

Effort by feel, not by pace

Because the efforts vary in length, they should vary in intensity too — a thirty-second effort should be faster than a two-minute one. Running everything at the same pace regardless of duration wastes the format.

This is genuinely easier without a watch showing pace. Fartlek is the one session where less data produces a better workout.

The Mona fartlek is attributed to Steve Moneghetti and is structured[1]; the others are conventional patterns. This timer's default randomises within a range.

Fartlek formats
Format Structure Total Character
Mona fartlek 2x90s, 4x60s, 4x30s, 4x15s, equal floats 20 min Structured, rising intensity
Classic unstructured Efforts as terrain suggests Varies By feel, no clock
Randomised (this timer) 30–180 s efforts, 60–180 s floats Varies Cannot be paced in advance
Pyramid 1-2-3-4-3-2-1 min with equal floats ~32 min Predictable, still varied
Short and sharp 10 x 30 s with 60 s floats 15 min Speed emphasis
  • Floats are easy running, not walking — recovering while still moving is where much of the adaptation comes from.
  • Vary intensity with effort length. A 30-second effort should be faster than a two-minute one.

Source: Mona fartlek — session associated with Steve Moneghetti, widely documented in distance running coaching literature

Sources

  1. Mona fartlek — session associated with Steve Moneghetti, widely documented in distance running coaching literature , Widely documented in running literature — accessed 2026-07-28

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❓ Frequently Asked Questions

What is fartlek?
Swedish for speed play — efforts of varying length and intensity with easy running between, traditionally taken as terrain suggests rather than to a plan. The variation is the training stimulus rather than an inconvenience.
Why does this timer randomise the intervals?
Because a fartlek where you know each effort is ninety seconds is an interval session in disguise, and you will pace it accordingly. Not knowing when the effort ends forces you to run by feel, which is the quality the session develops.
What is the Mona fartlek?
A structured session associated with Steve Moneghetti: 2x90s, 4x60s, 4x30s and 4x15s, each with an equal float, totalling twenty minutes. The descending effort lengths keep intensity rising through the session.
Should I walk during the recovery?
No — the recovery is easy running, which is what distinguishes fartlek from an interval session. If the floats are impossible to run, the efforts were too hard. Runners who stop are doing intervals with extra steps.
Should all the efforts be the same pace?
No, and running them that way wastes the format. A thirty-second effort should be faster than a two-minute one. Varying intensity with duration is what makes fartlek train pace change rather than one pace.
Should I look at my watch during a fartlek?
Preferably not. Fartlek is the one session where less data produces a better workout — running by feel is the point, and pace displayed on a wrist tends to flatten the variation the session is built on.
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