Fartlek: The Speed Play Workout

Fartlek. A Swedish word meaning "speed play." Invented in the 1930s, it's the ancestor of interval training—but in a free-form version, without a stopwatch or track. The principle: you alternate speed bursts and recovery periods by feel, depending on the terrain and your mood. Simple on paper, but trust me, it can be a tough workout.

Fartlek vs. Traditional Intervals

Structured interval training (10 × 400m, 5 × 1000m) is precise, measurable, and repeatable. Fartlek, on the other hand, is its complete opposite: the speed bursts vary, recoveries are unstructured, and the route changes. One isn't better than the other—they complement each other.

Track intervals are excellent for dialing in specific paces (like VO2 max pace or 10K race pace). Fartlek is better for developing your ability to change pace—exactly what we do during a race: accelerating uphill, responding to a surge, or re-accelerating after an aid station.

How to Structure a Fartlek Workout

Free-form Fartlek

The most classic approach: for 40-50 minutes, you alternate speed bursts lasting 30 seconds to 3 minutes with recoveries by feel. Intensity ranges from threshold pace to near-sprint, depending on your desire. This is the original version—and frankly, the most enjoyable. Personally, it's my favorite workout.

Structured Fartlek

For those who prefer some guidelines: 10 × (1 min fast / 1 min slow), or a pyramid of 1-2-3-4-5-4-3-2-1 minutes fast with equal recovery periods. This is a compromise between the freedom of Fartlek and the precision of interval training.

Terrain-based Fartlek

Use the landscape as your guide: accelerate on every uphill, recover on the downhill. Or sprint between two streetlights, then recover on the next stretch. The terrain dictates the session—and every run is different. It's perfect when you don't want to overthink things.

Who is it for?

Fartlek is great for beginners getting introduced to speed work (short bursts are less intimidating than a track session), for runners bored with traditional interval training, and for trail runners who rarely run on flat terrain. For experienced competitors, it remains an excellent transition tool between foundational phases and specific race preparation.

A GPS watch can enhance Fartlek by analyzing the paces achieved afterward—but be careful not to fall into the trap of staring at your watch during the session. That would kill the very spirit of the workout.