What is the difference between fartlek and interval training?

Both alternate hard and easy efforts, but structured interval training uses precise work and rest periods, for example four 4-minute efforts with 3-minute recoveries, while fartlek is unstructured and guided by feel or landmarks. Intervals are better for hitting exact training targets; fartlek is better for variety, learning pace, and running on varied terrain where fixed timing is awkward.

Is fartlek good for building VO2 max?

Yes. When the hard surges are genuinely hard, near 90 percent of maximum heart rate, fartlek delivers the same VO2 max stimulus as structured intervals, because time spent near your maximum is what drives the adaptation. It also improves running economy and teaches pace judgment. For the maximum VO2 max stimulus, structured protocols like the Norwegian 4x4 are more precise, but fartlek is a strong, flexible complement.

How do I do a fartlek workout?

Warm up with 10 minutes of easy running. Then alternate faster efforts with easy recovery jogs for 20 to 30 minutes, using landmarks or feel to decide when to surge and when to ease off, for example hard to the next lamppost, easy to the one after. Keep the surges strong but controlled, and finish with a 5-minute cool-down. There is no fixed formula, which is the point.

How often should I do fartlek training?

Once or twice a week is plenty, as part of a balanced running week that is mostly easy aerobic running. Because fartlek can include hard efforts, treat it like any interval session: keep at least 48 hours from your other hard days, and do not stack it on back-to-back days.

Fartlek Training: What It Is and How to Do It

Q: What is fartlek training?

Fartlek is a form of interval training where you vary your pace by feel during a continuous run, alternating faster bursts with easier recovery, without a fixed structure. The word is Swedish for speed play. Unlike track intervals with exact times and distances, fartlek is flexible: you might surge to the next tree, then jog until you recover, then surge again. It builds speed and aerobic fitness in a less rigid, more playful way.

By Cristian Serb · Updated September 6, 2026

A runner varying pace on an open road during a fartlek session

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Fartlek training is unstructured speed play: during a continuous run, you vary your pace by feel, alternating faster surges with easy recovery, without fixed times or distances. The word is Swedish for speed play. When the surges are genuinely hard, fartlek builds VO2 max and running economy just like structured intervals, but with more flexibility and less rigidity.

Fartlek is one of the oldest and most flexible forms of interval training, and it is perfect for runners who find track sessions too rigid. This guide explains what it is, how it differs from structured intervals, how to do it, and why it works.

What Is Fartlek Training?

Fartlek is a Swedish word meaning "speed play," developed in the 1930s by Swedish coach Gosta Holmer. The idea is simple: during a run, you play with your pace, surging hard for a stretch, then easing back to recover, then surging again, guided by how you feel or by landmarks rather than a stopwatch.

That makes fartlek a form of interval training, but a loose one. Where a track session prescribes exact efforts and rests, fartlek is spontaneous. You might sprint to the top of a hill, jog the descent, then run hard to a distant tree. It suits varied terrain and keeps running interesting.

Fartlek vs Structured Intervals

Both alternate hard and easy, but they serve slightly different purposes:

	Fartlek	Structured intervals
Structure	Unstructured, by feel or landmarks	Fixed work and rest times or distances
Best for	Variety, pace learning, varied terrain	Hitting precise training targets
Recovery	Jog, whenever you feel ready	Prescribed duration
Example	Hard to the next lamppost, easy to the one after	4 x 4 min hard, 3 min easy

Neither is better; they complement each other. Use structured protocols like the Norwegian 4x4 when you want a precise VO2 max stimulus, and fartlek when you want flexibility or a mental break from the track.

How to Do a Fartlek Workout

Warm up with 10 minutes of easy running.
Play with pace for 20 to 30 minutes: alternate hard surges with easy recovery jogs. Use landmarks (run hard to that sign, easy to the next) or just feel.
Keep the surges strong. For a VO2 max effect, the hard efforts should reach about 85 to 95 percent of your maximum heart rate.
Cool down for 5 minutes easy.

There is no fixed formula, which is the whole appeal. A beginner might surge for 30 seconds; an experienced runner might hold efforts for 2 to 3 minutes.

Example Fartlek Sessions

Landmark fartlek: on a route with regular features, alternate hard and easy between them for 25 minutes.
Pyramid fartlek: surges of 1, 2, 3, 2, 1 minutes hard, each followed by equal easy jogging.
Time fartlek: 8 to 10 surges of 1 minute hard, 1 minute easy, a structured cousin of true fartlek and an easy on-ramp.

Why Fartlek Works

When the surges are hard enough, fartlek accumulates time near your maximum, which is the driver of VO2 max improvement. A meta-analysis confirmed interval-style training raises VO2 max more than steady-state running (Milanovic et al., 2015). Fartlek also sharpens running economy and, because it is guided by feel, teaches you to judge effort and pace, a skill that pays off in races. For structured running interval plans, see our interval training for running guide.

Time Your Surges with PEAKVO2

If you want a little structure inside your speed play, PEAKVO2 runs interval patterns like 30/30 and the Norwegian 4x4 on iPhone and Apple Watch, with heart rate zones and a haptic tap at each switch, so your surges hit the right effort without watching a clock. Use it for the structured days and run free on the rest.

Run guided intervals with PEAKVO2

The Norwegian 4x4, 30/30, and more, on iPhone and Apple Watch, with automatic phases, a haptic tap at every switch, and heart rate zones. For the days you want structure. Three workouts free.

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References

Milanović Z, Sporiš G, Weston M. Effectiveness of High-Intensity Interval Training (HIT) and Continuous Endurance Training for VO2max Improvements: A Systematic Review and Meta-Analysis of Controlled Trials. Sports Med. 2015;45(10):1469-1481. PubMed
Helgerud J, Høydal K, Wang E, et al. Aerobic high-intensity intervals improve VO2max more than moderate training. Med Sci Sports Exerc. 2007;39(4):665-671. PubMed

Cristian Serb

I'm the developer of PEAKVO2. I built it because I was doing the Norwegian 4x4 myself and wanted the timing handled on my wrist so I could just train. I took my own VO2 max from about 41 to 51 with it. PEAKVO2 on the App Store.