Fartlek

Varied faster efforts inside a continuous run, with no track and no fixed structure.

Also called: speed play, unstructured intervals.

Fartlek — Swedish for "speed play" — is interval training without the arithmetic. Its real advantage is psychological: varied efforts on varied terrain keep you engaged in a way that a lap counter does not, and the lack of a target pace per rep means you run by feel, which is a skill worth practising for race day.

The session

Shown at a 4:00 marathon reference — 47 min total, about 7.6 km, including 25 min of quality work.

Warm-up

  1. 12 min easy (6:43–7:24/km)

Main set

  1. 3 min @ 4:48/km (5K)
  2. 60 s float @ 6:43/km (easy)
  3. 45 s @ 4:48/km (5K)
  4. 2 min float @ 6:43/km (easy)
  5. 90 s @ 5:04/km (10K)
  6. 90 s float @ 6:43/km (easy)
  7. 3 min @ 4:48/km (5K)
  8. 2 min float @ 6:43/km (easy)
  9. 2 min @ 5:04/km (10K)
  10. 2 min float @ 6:43/km (easy)
  11. 2 min @ 4:48/km (5K)
  12. 90 s float @ 6:43/km (easy)
  13. 60 s @ 5:14/km (T)
  14. 2 min float @ 6:43/km (easy)

Cool-down

  1. 10 min easy (6:43–7:24/km)

Why this session works

Unstructured speed-play: surges of varying length at varying effort with easy floats. Touches several systems in one run and keeps training honest fun.

Source: Seiler 2010. Training phase: build.

Run it at your own paces

Open the workout generator and enter a recent race time — every rep length, recovery and target pace is recalculated for your fitness, and the session exports to .fit for a Garmin watch.

Frequently asked questions

What is a fartlek?

Varied faster efforts inside a continuous run, with no track and no fixed structure. Fartlek — Swedish for "speed play" — is interval training without the arithmetic.

How long is this session?

At a 4:00 marathon reference it comes to 47 min and about 7.6 km, of which 25 min is prescribed quality work. The generator scales both to your own paces, so a faster runner covers more ground in the same time.

Who is this workout for?

It is written for the build phase of a marathon build. The distances shown suit a 4:00 marathoner; enter your own recent race time in the generator and every rep length and target pace is recalculated for you.

More fartlek and combination sessions

  • Mona fartlek — A fixed 20-minute sequence of hard efforts with equal float recoveries, descending in length.
  • 10-20-30 workout — Repeated cycles of 30 seconds easy, 20 seconds moderate and 10 seconds near-sprint.
  • Combination workout — Threshold, then interval, then repetition work in a single session — three gears in one run.
  • Cutdown blocks — Long blocks that shorten and speed up through the session.

See all 32 sessions in the library.