fartlek

American  

[fahrt-lek] / ˈfɑrt lɛk /

noun

1. a training technique, used especially among runners, consisting of bursts of intense effort loosely alternating with less strenuous activity.

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fartlek British  

/ ˈfɑːtlɛk /

noun

1. sport another name for interval training

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Etymology

Origin of fartlek

1950–55; < Swedish fart speed + lek play

Explanation

A fartlek is a fun workout that combines short bursts of fast or intense movement with periods of easier exercise. The word fartlek comes from Swedish, meaning "speed play." It’s a training method for runners and other athletes in which they alternate between varying intensities of effort in one continuous exercise. Instead of sticking to a strict plan, athletes can sprint when they feel like it and slow down when they need to catch their breath. This mix of intensity levels keeps their run dynamic and engaging, allowing them to listen to their bodies while still challenging themselves.

Example Sentences

This simple approach is a classic form of fartlek training.

From Science Daily • Oct. 20, 2025

“It always feels like a fartlek out there,” Obiri said, referencing a training system for distance runners in which terrain and pace are varied in an effort to tamp down boredom.

From Seattle Times • Apr. 17, 2023

No need to check your heart rate or track each interval’s length, in time or distance, said Dr. Wisloff, who also trains with fartlek.

From New York Times • Nov. 10, 2021

In other words, you have to do a lot of sprinting – even if, like me, you hate it – or mix it with slower running in what’s known as fartlek.

From The Guardian • Jan. 1, 2019

Even though we felt as if our hearts were in our throats, Neile and I enjoyed our fartlek workout so much we thought we might try it again the next morning.

From Washington Post • Aug. 31, 2015