Fartlek (Speed Play)

What fartlek does

A fartlek alternates faster surges with easy running, and nothing is prescribed in advance. You pick where each surge ends by a landmark, a song, a count of seconds or how you feel, then jog easy until you are ready for the next one. You can shorten or lengthen the session on the day.

The surges give you time at a harder effort, and the easy running between them lets you do it again. Short pickups teach you to run fast and relaxed. Surges of one to three minutes at a hard effort work the way intervals do (see the guide on interval workouts). Because you choose the surges, a fartlek is also a session you can win when you are rebuilding: pick it over a long tempo, or over mile repeats.

Where it fits

Short pickups and long surges do different jobs, and they sit in different places in your week:

• Pickups of 15 to 30 seconds inside an easy run work like strides, and they can go in a couple of runs a week. See the guide on strides.
• Surges of 45 seconds to a few minutes at a hard effort are a hard session. Count it in your two a week, and never put it next to another hard workout.
• 5K and 10K: one feel-good-fast session a week, built from pickups of 45 seconds to a minute or from 200s on a track.
• Marathon: early in a build, fast but not very tiring fartlek comes first, 16 to 12 weeks out, while the long run and the mileage build with little intensity in them. In the taper, keep one or two key workouts a week, which can be marathon pace, tempo or a fartlek, and do not make them hard.
• Rebuilding after time off: after a month or two of easy running, add one weekly workout (fartlek, hills or tempo) at reduced volume.

How hard to run the surges

Hard but not all out: about 7 out of 10. In 17 active adults, 3-minute intervals run at 7 or 8 on a 0 to 10 effort scale gave more time near maximal oxygen uptake than intervals at 6, with no difference between 7 and 8¹. So 7 is enough, and 8 gave no more. A fast session should finish at 6 or 7 out of 10, not 9 or 10.

Do not run every surge flat out, and on surges of about a minute dial the effort back a notch. Running by feel can drift harder on a fresh day, so build into the session and do not make the first surge the hardest one.

What a session looks like

Warm up with easy running and a few strides, then start the surges inside the run. The size of the session grows with experience:

• Rebuilding or newer: four or five surges of 30 seconds inside a 30-minute easy run.
• Your first step past strides: after three to four weeks of comfortable strides, an occasional session of 30-second pickups with 1 to 1.5 minutes of easy running between.
• Recreational 5K and 10K runner: 1 minute on and 1 minute off, 45 seconds on and 15 off, or 90 seconds on and 30 off, at roughly half marathon, 10K or 5K effort. Short surges let you correct your pacing as you go.
• Experienced marathoner early in a build: 1 minute on and 1 minute off, or 2 minutes on and 90 seconds off, at roughly 3K to 10K effort.