Turning every surge into a sprint
Only the 30 seconds go faster than vVO₂max. The rest sit between threshold and vVO₂max: attack every surge flat out and you reach the 4-minute one empty, and the fartlek becomes a grind.
RunningVO2maxIntermediate 52 min
Fartlek: six surges of 30 seconds to 4 minutes in an easy run
A fartlek run, or 'speed play': an easy run with six surges of 30 seconds to 4 minutes at varied paces, never stopping in between. 52 minutes in all, including 11 minutes 15 of efforts. A playful session for regular runners.
Session profile16 blocks
At a glance
- Duration
- 52 min
- Main target
- 86–115%vVO₂max6 Z6 · Anaerobic
- Time at target
- 11 min
- Estimated load
- 55
- Structure
- 2′ at 92–98% vVO₂max + 1′30 at 60–66% vVO₂max + 1′ at 98–102% vVO₂max + 2′ at 60–66% vVO₂max + 3′ at 90–94% vVO₂max + 1′30 at 60–66% vVO₂max + 30″ at 105–115% vVO₂max + 1′30 at 60–66% vVO₂max + 45″ at 100–104% vVO₂max + 2′30 at 60–66% vVO₂max + 4′ at 86–91% vVO₂max + 2′ at 60–66% vVO₂max
- Level
- Intermediate
- Equipment
- GPS watch
The session in detail
vVO₂max
Time in zone
- Z131 min
- Z210 min
- Z47 min
- Z54 min
- Z61 min
What the targets mean
| Target | Zone | Time | vVO₂max 14 km/h | vVO₂max 16 km/h | vVO₂max 18 km/h |
|---|---|---|---|---|---|
| 105–115% | 6Anaerobic | 1 min | 4:05/km–3:44/km 123–134 m per rep | 3:34/km–3:16/km 140–153 m per rep | 3:10/km–2:54/km 158–173 m per rep |
| 100–104% | 5VO₂max | 1 min | 4:17/km–4:07/km 175–182 m per rep | 3:45/km–3:36/km 200–208 m per rep | 3:20/km–3:12/km 225–234 m per rep |
| 98–102% | 5VO₂max | 1 min | 4:22/km–4:12/km 229–238 m per rep | 3:50/km–3:41/km 261–272 m per rep | 3:24/km–3:16/km 294–306 m per rep |
| 92–98% | 5VO₂max | 2 min | 4:40/km–4:22/km 429–457 m per rep | 4:05/km–3:50/km 491–523 m per rep | 3:37/km–3:24/km 552–588 m per rep |
| 90–94% | 4Threshold | 3 min | 4:46/km–4:34/km 630–658 m per rep | 4:10/km–3:59/km 720–752 m per rep | 3:42/km–3:33/km 810–846 m per rep |
| 86–91% | 4Threshold | 4 min | 4:59/km–4:43/km 803–849 m per rep | 4:22/km–4:07/km 917–971 m per rep | 3:53/km–3:40/km 1032–1092 m per rep |
| 60–66% | 1Recovery | 11 min | 7:09/km–6:30/km | 6:15/km–5:41/km | 5:33/km–5:03/km |
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What this session is for
A fartlek takes you through the whole range of paces in a single run: threshold on the 4-minute surge, vVO₂max on the 1- to 2-minute ones, a touch faster still over 30 seconds. No single intensity lasts long enough to replace a proper threshold or VO₂max session. What the mix does work on is something those sessions rarely touch: changing gear, kicking again, then recovering while still running.
It's a session for the head, too. No track, no stopwatch to the second: Gösta Holmér's idea, in the Swedish forests of the 1930s, was to run fast because the ground and the mood invited it. No study has measured the effects of fartlek in this form: it's historical practice, not a tested protocol.
Who it's for
Regular runners who train off-road, or who switch off the moment anyone mentions a stopwatch. A beginner can borrow the idea in a gentle version: two or three slower surges, without the fast 30 seconds. You need a recently measured vVO₂max for the template to land right; without one, run by feel, which is the spirit of fartlek anyway.
When to do it
A fartlek can replace your weekly VO₂max or threshold session, or alternate with it: once a week is a common guideline. It suits a comeback after a break, or a week when one more timed session feels like too much. Put it after an easy day or a rest day, never the day before a long run or a race. To progress, lengthen the surges or add more, or move to the free-form 40-minute version.
How to do it
Warm-up
20 min10′ at 60–65% vVO₂max + 5′ at 66–72% vVO₂max + 5′ at 66–74% vVO₂max
10 minutes of easy running at 60–65% of vVO₂max, then 5 minutes at 66–72% and 5 minutes at 66–74%, a slightly livelier easy run. The warm-up is longer than usual: the first surge comes quickly, and the fastest lands mid-session.
Main set
22 min2′ at 92–98% vVO₂max + 1′30 at 60–66% vVO₂max + 1′ at 98–102% vVO₂max + 2′ at 60–66% vVO₂max + 3′ at 90–94% vVO₂max + 1′30 at 60–66% vVO₂max + 30″ at 105–115% vVO₂max + 1′30 at 60–66% vVO₂max + 45″ at 100–104% vVO₂max + 2′30 at 60–66% vVO₂max + 4′ at 86–91% vVO₂max + 2′ at 60–66% vVO₂max
Six surges, each followed by easy running at 60–66% of vVO₂max:
- 2 min at 92–98%, then 1 min 30 easy;
- 1 min at 98–102%, then 2 min;
- 3 min at 90–94%, then 1 min 30;
- 30 sec at 105–115%, then 1 min 30;
- 45 sec at 100–104%, then 2 min 30;
- 4 min at 86–91%, then 2 min.
At 16 km/h, the efforts run from 4:22 to 4:07/km over 4 minutes up to 3:34 to 3:16/km over 30 seconds, and the easy running from 6:15 to 5:41/km. Never stop between surges. If a drag or a bend comes up mid-surge, hold the effort rather than the pace.
Cool-down
10 min10′ at 55–65% vVO₂max
10 minutes of very easy running at 55–65% of vVO₂max. If the 4-minute surge, the last one, felt harder than the 3-minute one, that's normal: it comes at the end, on legs that are already tired.
How it should feel
Changeable, and that's the fun of it: 3 out of 10 on the easy stretches, 8 out of 10 at the end of the fast 30 seconds. You never have time to get bored, or to settle into the hurt. The last surge, 4 minutes at threshold, asks for patience more than speed.
Common mistakes
Stopping between surges
The easy running between surges is part of the session: it's what teaches you to recover on the move. Slow down as much as you need, but don't walk or stop.
Following the template to the second
The template is a starting point. If a hill turns up just right for the 3-minute surge, take it; if you're tired, cut it short. Sticking to the clock against the terrain loses what makes fartlek worth doing.
Adding it to an already full week
A fartlek replaces a hard session; it doesn't sit on top of one. The surges feel short, but they add up: count it in your week as a proper session.
When to skip it
Before you start
- Being able to run 45 minutes easy without difficulty.
- A recently measured vVO₂max, or being used to running by feel.
Skip it if
- You have pain or a recent injury.
- A long run or a race is planned for the next day.
Origin and evidence
Level of evidence
Established practice, no dedicated studyLevel 1 of 5
Fartlek is credited to Gösta Holmér, a Swedish coach of the 1930s and former decathlete, bronze medallist at the 1912 Olympics (Athletics Weekly). His athletes Gunder Hägg and Arne Andersson set several world records in the 1940s. Secondary sources disagree on Holmér's exact session, and fartlek never had a numerical prescription: that's the whole idea. The template, its durations and intensities, the warm-up and the cool-down are Wattson choices. No study of fartlek in this form was found. Bottom line: well-documented historical origin, effects not measured.
Sources
- Athletics Weekly (Gösta Holmér, fartlek)
Frequently asked questions
What is a fartlek run?
'Speed play' in Swedish: an easy run with surges of varied length and pace, without stopping between them. It's credited to Gösta Holmér, a Swedish coach of the 1930s. The original fartlek had no fixed structure; this template offers one, to follow or adapt.
How fast should a fartlek be?
It changes with each surge. Here, from 86–91% of your vVO₂max over 4 minutes to 105–115% over 30 seconds, with easy running at 60–66% in between. At 14 km/h that's 4:59 down to 3:44/km; at 18 km/h, 3:53 down to 2:54/km. The shorter the surge, the faster it goes.
Fartlek or interval training?
Intervals repeat the same effort at the same pace, often on a track, with set recoveries. A fartlek mixes lengths and paces, and the recoveries are run. The first works on one specific quality; the second, on changes of pace. Both have a place, in alternation.
Can you do a fartlek without a watch?
Yes, that's its original form. Pick your surges from the terrain, to a tree, a bend or the top of a hill, and judge the effort by feel: strong on the long ones, sharp on the short ones. A watch mainly helps you follow a template like this one.
Is fartlek good for beginners?
Yes, in a gentle version: two or three slower surges, without the fastest efforts, in an easy run you can already manage. It's often a better first taste of faster running than track intervals: there's no set clock and no standing recoveries.
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