If you’ve spent any time around runners, you may have heard the term fartlek tossed around—often followed by a stifled laugh. And fair enough. The word sounds like a punchline. But behind the jokes is one of the most effective (and surprisingly fun) running workouts out there.

So, what exactly is a fartlek run? How do you do one? And why should you consider adding it to your training plan? Whether you’re preparing for your first 5K or need to add variety to your routine, fartlek training can help improve both speed and endurance.

First of all… what does “fartlek” mean?

Let’s get the name out of the way. Fartlek is a Swedish word that translates to “speed play.” It was developed in the 1930s by Swedish coach Gösta Holmér as a way to build endurance and speed for cross-country runners.

Unlike strict interval training—where you run to the whistle or follow a rigid pace chart—fartlek runs are unstructured and based on feel. It’s running with spontaneity, alternating between faster and slower paces throughout a session, with no hard rules. You can sprint to that lamppost, jog to the corner shop, then pick up the pace again until your playlist changes. It’s speed training with freedom.

How does a fartlek run work?

A fartlek run typically starts with a warm-up jog, followed by a series of faster bursts and slower recovery periods—often guided by landmarks, time, or effort. The beauty is in the flexibility. Here’s a basic example:

• 10-minute easy jog to warm up
• Pick up the pace for 1 minute (moderate to hard effort)
• Jog for 2 minutes
• Sprint for 30 seconds
• Jog until you reach a streetlight or tree
• Repeat with variations for 20–40 minutes
• Cool down with 5–10 minutes easy running

Fartlek training can be as casual or as structured as you want. Some runners follow formal patterns (like 2 minutes fast, 1 minute slow), while others rely on what feels right. The key is to keep switching gears.

The benefits of fartlek training

Fartlek runs might sound playful (and they are), but don’t mistake them for slacking off. This training method offers a potent mix of aerobic and anaerobic benefits.

1. Improved speed and endurance

By mixing faster and slower running intervals, you teach your body to adapt to different paces, improving both cardiovascular fitness and muscular strength. One 2020 study in the Journal of Strength and Conditioning Research found that unstructured interval training like fartleks can enhance VO₂ max and running economy—two key markers of endurance.

2. Mental toughness

Without the structure of a timer or set interval, you have to rely on internal motivation and body awareness. It builds resilience and teaches you to stay comfortable with being uncomfortable.

3. Breaks the monotony

Let’s face it—running the same route at the same pace can get boring. Fartleks inject spontaneity into your training, helping you stay mentally fresh and engaged.

4. Lower risk of injury

Compared to high-intensity intervals or track workouts, fartlek runs can be gentler on the joints. Because you control the effort and recovery, there’s less pressure to push beyond your limits.

Who should do fartlek runs?

The short answer? Pretty much everyone.

• Beginner runners can use fartleks to learn pacing and improve aerobic capacity without the stress of strict plans.
• Intermediate and advanced runners can use fartleks to fine-tune race pace, build stamina, or recover from harder speed sessions.

They’re also great during race taper weeks or in the off-season, when you want to maintain fitness without overtraining.

Tips for your first fartlek run

1. Start with time or landmarks. Use music tracks, streetlights, or lampposts to guide your pace changes.
2. Keep it playful. Don’t stress about pace. Run hard enough to get out of breath, then recover until you feel ready to go again.
3. Use fartleks for race prep. Simulate pace changes you might experience in a race (like hill surges or mid-race breakaways).
4. Try group fartleks. Take turns calling out when to speed up and slow down. It adds fun and unpredictability.

Sample fartlek workouts

Beginner fartlek

• 5 min jog warm-up
• 30 sec faster run / 1.5 min jog (x6)
• 5–10 min cool down

Intermediate fartlek

• 10 min jog warm-up
• 2 min hard / 2 min easy (x5)
• 5 min jog
• 1 min sprint / 1 min jog (x3)
• 5 min cool down

Advanced pyramid fartlek

• 10 min warm-up
• 1 / 2 / 3 / 4 / 3 / 2 / 1 min fast intervals, equal recovery jog between
• 10 min cool down

Fartlek runs vs interval training: what’s the difference?

It’s easy to confuse fartlek runs with interval training—they both involve alternating speeds, after all. But there’s a key distinction. Interval training is structured: it’s typically time- or distance-based, and each repeat is performed at a specific intensity, often with measured rest periods.

Fartlek runs are more fluid. You might sprint to the next post box just because you feel like it, then jog until you catch your breath. Think of interval training as the disciplined older sibling, and fartlek as the free-spirited one. Both have their place in a runner’s toolkit, but fartleks are often easier to integrate into everyday running without needing a track or timer.

How often should you do fartlek runs?

How often you include fartlek training in your routine depends on your goals and fitness level. For most runners, once a week is a solid starting point. It adds variety without overwhelming your schedule or risking overtraining.

If you’re building towards a race or feeling plateaued, you might try incorporating fartlek-style efforts twice weekly—perhaps replacing a tempo run or steady-state session. Just be sure to give your body time to recover between harder workouts, especially if you’re also doing long runs or hill sessions.

Can you do fartlek runs on a treadmill?

Absolutely. While fartlek runs are often associated with outdoor spontaneity, they translate well to the treadmill. You can adjust speed manually to mimic varied pace changes—for example, alternate between running at 12 kph for 1 minute and 9 kph for 2 minutes. You could even play around with incline for an added challenge.

To keep it fun and less robotic, try using a playlist as your guide: sprint during the chorus, recover during the verse. Or use a random-number generator app to surprise yourself with different paces and durations. Make sure to use appropriate running sneakers too.

Fartlek training for marathon preparation

If you’re training for a marathon, you might assume fartlek runs are more suited to 5K or 10K prep—but they’re surprisingly effective for long-distance races too.

In the early stages of a half-marathon or marathon training plan, fartlek workouts help build a strong aerobic base while keeping things mentally engaging. As your mileage increases, they can be used to mimic race-day pace changes—think surges to overtake crowds, rolling hills, or fluctuating energy levels.

One strategy is to integrate fartlek intervals into your long runs. For example, after an easy 60 minutes, you might include 6 x 3-minute surges at marathon pace or slightly faster, with 2 minutes easy in between. This helps train your body to recover while still moving, which is crucial for the later stages of a race.

They also come in handy during marathon taper weeks, when you want to stay sharp without overtaxing your legs. A short, light fartlek session can provide enough stimulus without the wear and tear of a full tempo run.

Fartlek training might not come with the same level of data tracking and structure as other types of speed work, but it invites runners to listen to their bodies, push boundaries in the moment, and reconnect with the joy of running.

So next time you’re lacing up and feeling uninspired, try tossing a fartlek into the mix. It might sound silly—but it runs seriously well.