Fartlek Training: Speed Workouts for Runners

Fartlek is an unstructured speed workout: you alternate faster and slower running by feel, instead of following set distances or times. It's a gentle way for beginners to start speed work, because you decide how hard to push, which lowers the injury risk of jumping into a rigid programme too soon. Below: how fartlek compares to other speed workouts, a step-by-step beginner session, how it fits into your training plan, what it does to your body, a first month of sessions, choosing terrain, helpful tools, and named fartlek workouts for runners who like structure.

Have you fartlekked recently?

I'm not trying to be rude — fartlek is Swedish for speed play.

Warm up, run faster for a while, slower for a while, repeat as many times as you like, then cool down. That's it. Faster running and slower running, mixed together, without rigid structure.

I used to hate fartleks. I never did them.

I wanted structure. I didn't like heading out and deciding on the spot how fast to go and for how long — because every fartlek session differs, and I needed that comparison to track progress. In the last few years I've mellowed. I'm less number-bound. I've learned that sometimes an unstructured session is exactly what you need.

Depending on your personality, you'll either love that or hate it.

The playful nature makes fartlek fun. It helps you connect with your body. That's why I recommend it for beginners wanting to try speed work — you decide, based on how you feel, how hard you'll push. Jump into a rigid structured speed programme before you're ready and you risk injury. With fartlek, that risk is smaller.

How Fartlek Compares to Other Speed Workouts

Here's what you need to know about how fartlek stacks up against other speed work:

Fartlek gives you flexible structure with effort levels that vary between 5K–10K pace. You recover by floating — not jogging slowly, but maintaining a purposeful rhythm. Perfect when you're introducing speed work or want to break training monotony.

Intervals lock you into fixed distances and times at specific paces, usually 3K–5K effort with complete rest between efforts. They develop your maximal oxygen uptake (VO2 max) and speed — but demand more from your body.

Tempo runs hold one steady effort at your threshold pace with no recovery during the effort portion. They build your lactate threshold — the pace you can hold for an hour flat out.

Track repeats require precise distances and very specific paces with timed recovery. They develop pure speed and race preparation.

Hill repeats use uphill efforts at RPE-based intensity with downhill jog recovery. They build power, strength, and running form simultaneously.

With fartlek, you're not locked into one intensity. Some efforts might hit 90% of your maximum heart rate, others 85%. That variation trains different parts of your aerobic and anaerobic systems within a single session — while your mind stays relaxed about hitting exact splits. For more structured approaches to speed training for runners, fartlek serves as a perfect bridge between easy running and formal interval running sessions.

Step-by-Step Beginner Fartlek Session

When you start out, do a solid warm-up, then pick a landmark and run to it at a higher effort. Simple as that.

Total time: 35–45 minutes

Warm-up (10–15 minutes):
Start with 5 minutes easy running. Add 4–5 dynamic movements — leg swings, high knees. Gradually build pace to a comfortable running rhythm.

Main Set (15–20 minutes):

Pick a landmark 200–400m ahead — a street light, mailbox, or tree. Run to it at 7/10 effort. You should be breathing harder but able to say a few words. Float for 1–2 minutes at 5/10 effort — keep moving, this isn't a jog. Repeat 6–8 times, varying your landmarks and efforts.

Cool-down (10 minutes):

Drop back to easy running, then finish with light stretching.

Pacing guidelines:

Your fast efforts should feel comfortably hard — around 10K effort, or roughly 5K to 10K effort — rather than tied to a fixed gap from your easy pace. Your float pace should be 15–20 seconds per mile faster than your easy pace. If you can't say anything at all during the fast efforts, back off.

Your first session might cover 3–4 miles total. That's perfect. Focus on the rhythm — fast, float, fast, float — not the distance.

Not sure you're ready to step up from easy running? Run through my speed training readiness checklist first — it takes a couple of minutes and saves you guessing.

How Fartlek Fits Into Your Training Plan

Fartlek fits differently into your running training depending on your current phase:

During base building (8–12 weeks): I'd recommend one fartlek per week maximum. Keep efforts controlled at 6–7/10 intensity. Focus on teaching your body to change pace smoothly, with sessions of 15–20 minutes of quality work. During this phase, fartlek complements your base running development perfectly.

In your build phase (6–8 weeks): Fartlek becomes more structured. I'd suggest introducing named sessions like Mona or Moose fartlek. Efforts can reach 8/10, with sessions lasting 20–30 minutes of quality work.

During peak sharpening (3–4 weeks): Short, sharp fartlek sessions work brilliantly here. Mix race-pace efforts with faster surges — perfect for practising race tactics. Keep sessions to 15–25 minutes of quality work.

In recovery or off-season: Go completely free-form. Run entirely by feel. It's a sensible way to maintain fitness without pressure.

The trick is using fartlek as a bridge. Not ready for intervals? Try fartlek. Too structured for your current mindset? Fartlek's got you covered.

Training for a race? PlanMyRace builds a personalised week-by-week plan around your race date, current fitness and the days you can train, for any distance from 1500m to the marathon. Your first week is free.

What Fartlek Does to Your Body

Fartlek hits multiple parts of your fitness simultaneously. That's what makes it so effective.

Your oxygen system improves:

Your maximum oxygen uptake gets better because you're pushing into that 5K–10K effort range repeatedly. The varied pace forces your heart and lungs to adapt quickly — increasing your ability to deliver oxygen to working muscles. Some efforts might hit 90% of your max heart rate, others 85%.

Your lactate clearance gets better:

Those floating periods between fast efforts aren't just recovery — they teach your body to clear lactate more efficiently while running at a decent pace. You can address a running plateau significantly just by getting better at the float portions of your fartlek sessions.

Your race brain develops:

Here's where fartlek really shines. You're making pace decisions constantly throughout the session — should I surge now? Can I hold this to the next tree? How hard should I go up this hill? That decision-making under fatigue builds the exact mental skills you need for racing.

Your pace changes get smoother:

Constant pace changes improve your running efficiency. Your body learns to shift gears smoothly, recruiting different muscle fibres as needed. The result — better race performance when you need to respond to moves or vary your pace tactically.

Your First Month of Fartlek Training

Here's how I'd recommend you build up through your first month:

Week 1 — Foundation: Start with landmark fartlek as described above. Keep your quality time to 15 minutes at 6–7/10 intensity. Take 2–3 easy days between sessions.

Week 2 — Extension: Try 8–10 efforts of 45–90 seconds. Build your quality time to 18 minutes at 6–7/10 intensity. Float for 60–90 seconds between efforts.

Week 3 — Intensity: Attempt pyramid fartlek — 1–2–3–2–1 minutes. Your quality time reaches 20 minutes at 7–8/10 intensity. Include one longer 3-minute effort to build endurance.

Week 4 — Structure: Try modified Mona fartlek: 2 x 60s fast + 60s float, 4 x 45s fast + 45s float, 4 x 30s fast + 30s float. Quality time, floats included, is about 14 minutes at 7–8/10 intensity — shorter than Week 3, but sharper.

Look for these signs of progress: Week 1, focus on completing the session comfortably. Week 2, maintain pace better during longer efforts. Week 3, handle the intensity without your form breaking down. Week 4, float effectively — not jogging slowly.

Each week should feel challenging but achievable. If Week 2 feels too difficult, repeat Week 1. Build up progressively.

Choose Your Terrain Wisely

Your terrain choice completely changes the fartlek experience. Different surfaces work for different training goals:

Road Fartlek:

Perfect for pace awareness and speed development. Use landmarks like streetlights, intersections, or buildings. The consistent surface lets you focus purely on effort and pace. I'd recommend this for beginners learning to judge effort levels.

Trail Fartlek:

Brilliant for strength building and mental toughness. Hills naturally vary the intensity while the softer surface reduces impact stress — and they force you to run by effort, not pace.

Track Fartlek:

Ideal for precision and speed work. Use the straights and curves to structure efforts. Easy to measure progress by counting laps. Other runners provide natural competition.

Beach/Sand Fartlek:

Excellent for power development and injury prevention. Sand provides resistance while the unstable surface improves your balance and stability. Lower impact on joints too.

Park/Grass Fartlek:

Great for form development and fun. The softer surface encourages longer strides, natural obstacles create variety, and it's perfect for group training.

Match terrain to your current needs. Feeling beat up? Hit the trails. Need speed work? Stick to roads or track.

Tools That Actually Help

Fartlek works brilliantly completely freeform — but sometimes you want a bit of guidance. Here are my recommendations:

Smartphone Apps:

Runkeeper offers custom interval workouts with audio cues. Strava's segment hunting creates natural fartlek opportunities. Nike Run Club provides guided speed runs with coaching. Adidas Running includes interval training programmes.

Low-Tech Options:

Create music playlists with fast songs for efforts and slower tracks for floats. Use podcasts and change pace during different segments. Train with a running partner and take turns calling out effort changes. Try a heart rate monitor and use HR zones instead of pace. Interested in zone-based training? I cover this thoroughly in heart rate zone training for a first 10K or half marathon.

Online Resources:

Running forums often share creative fartlek sessions. YouTube has guided fartlek workouts you can follow. Training websites offer downloadable fartlek plans.

The trick is picking the tool you'll actually use consistently. Don't let technology complicate what should be playful training.

Named Fartlek Workouts for Structure Lovers

Some of us need structure. Here are proven fartlek sessions with names and reputations:

Mona Fartlek (Steve Moneghetti):

Steve Moneghetti is a famous Australian marathon runner who won several big marathons and picked up medals at the Commonwealth Games and World Championships. The session is named after him, and he reportedly ran it regularly. The workout: 2 x 90 seconds fast + 90 seconds float, 4 x 60 seconds fast + 60 seconds float, 4 x 30 seconds fast + 30 seconds float, 4 x 15 seconds fast + 15 seconds float. This is tough. The key skill is learning to float — not jog — between efforts.

Moose Fartlek (Julian Spence):

5 sets of 3 minutes at 10K–HM effort + 1 minute jog + 1 minute at 5K effort + 1 minute jog. That's 30 minutes of quality work. The contrast between the longer threshold efforts and shorter speed bursts is brilliant for race preparation — especially when training for a half marathon.

Portsea Fartlek:

3 x 5 minutes fast + 1 minute float, 3 x 3 minutes fast + 1 minute float, 4 x 1 minute fast + 30 seconds float. That's 36 minutes of quality — definitely advanced territory. I've used this as part of half marathon and marathon preparations.

Michigan Fartlek:

1–2–3–4–3–2–1 minute pyramid with equal recovery between each effort. Perfect for building both speed and endurance.

Kenyan Hills Fartlek:

2 minutes moderate uphill + 1 minute easy downhill, repeated 8–10 times. Builds power and teaches efficient downhill running.

Elite athletes tested each of these. Don't let that intimidate you — adjust the speeds, times, and intensities to match your current fitness level.

Common Fartlek Mistakes and How I'd Fix Them

I see these fartlek mistakes frequently. Here's how I'd recommend avoiding them:

Running the "fast" parts too fast:

You turn every effort into an all-out sprint, then struggle to maintain any quality for the float portions. Use the talk test — during fast efforts, you should be able to say 3-4 words with some difficulty.

Floating too slowly:

The floats become slow jogs or walks, which defeats the purpose. Float pace should be roughly your normal training pace — maybe slightly easier, but still purposeful running.

Making every session different:

While variety is good, having zero consistency makes it impossible to track improvement. Use a core session like Mona fartlek once every two weeks, then vary your other fartlek sessions.

Skipping the warm-up:

You jump straight into fast running without proper preparation. Always start with 10-15 minutes of gradual warm-up. Your first fast effort should feel controlled and smooth.

Going by pace instead of effort:

You get fixated on hitting certain splits rather than running by feel. Cover your watch during fartlek sessions. Learn to judge effort by breathing, muscle tension, and overall sensation.

Doing fartlek too often:

Because it feels less structured, you think you can do it more frequently than other speed work. I'd recommend treating fartlek like any quality session — once or twice per week maximum.

Your Fartlek Questions Answered

How fast should I run the "fast" parts of a fartlek? Run by effort, not pace. On a scale of 1-10 where your easy pace is about 4-5, your fartlek efforts should be 7-8. You should be breathing harder but not gasping. If you can chat normally, go a bit faster. If you can't say anything, back off.

How often can I do fartlek workouts? I'd recommend treating fartlek like any speed work — once or twice per week maximum. You need recovery days between quality sessions. A typical program includes one structured speed session (intervals or tempo) and one fartlek per week.

Is fartlek better than regular interval training? They serve different purposes. Fartlek is brilliant for beginners, mental freshness, and learning to run by feel. Intervals work better for specific pace work and measurable progression. Both belong in sensible training programs.

Can I do fartlek during marathon training? Absolutely. Fartlek helps you practise surging and responding to moves during races. It also breaks up the monotony of long runs. Try adding 10-15 minutes of gentle fartlek in the middle of your long runs.

What if I can't maintain the float pace between efforts? That's normal when starting out. Your aerobic system is still developing. It's better to jog slowly and complete the session than to stop completely. Gradually work on making your recovery pace faster over several weeks.

How do I know if I'm improving at fartlek? For unstructured sessions, you'll notice running faster efforts feels easier. After your cool-down, complete some light running stretches to help with recovery and maintain flexibility for your next session.

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