Fartlek is a Swedish word meaning speed play. It’s a simple, natural form of speed training that can be worked into any daily run. During a run of a given distance, you accelerate - to the next telephone pole, to the end of the block, to any landmark. When you have pushed as long and as fast as you want (or can) you jog to recover. Then wehn you feel like it, you take off again.

Fartlek is speed training at your own pace. It is intuitive, free-form, without prescribed distances or speeds. You can run according to how you feel on that day, at that moment. Fartlek is speedwork but it can be playful and creative.

Variations include hill fartlek and timed segments.

See more definitions in the Definitive Guide to Running Terms.