What does the term 'Fartlek' mean in Swedish?

The Swedish term ‘Fartlek’ means “speed play.” It describes a running workout that alternates faster and slower efforts, usually without the rigid timing of formal interval training.

Swedish coach Gösta Holmér developed Fartlek in the late 1930s for cross-country runners. Sweden’s distance athletes had struggled against Finland’s highly successful runners, including Paavo Nurmi, so Holmér sought a method that combined endurance running with bursts faster than race pace.

Traditional Fartlek sessions often take place on natural terrain. A runner might accelerate between trees, surge uphill, or run hard for a chosen stretch before easing off to recover. The athlete or coach can adjust the effort according to terrain and how the body feels.

Fartlek is often confused with interval training, but the two are not identical. Intervals normally prescribe exact distances, speeds, repetitions, and recovery periods. Fartlek is more flexible and keeps the runner moving continuously. The method can also be adapted to cycling, swimming, and other sports, where changes in intensity create the same “speed play” effect.