Fartlek vs Tempo Run: Which One Should You Do?

Two of the most commonly recommended speed workouts for distance runners are the fartlek and the tempo run. Coaches prescribe both. Training plans include both. And runners regularly confuse them, run them interchangeably, or avoid one entirely because they are not sure what it actually is.

They are not the same workout. They produce overlapping benefits through different mechanisms, suit different phases of training and different types of runners, and asking which one you should do is a bit like asking whether you should eat breakfast or lunch. The honest answer is usually both, at different times and for different reasons.

This article explains what each method is, how they differ, what each one does well, and when to use which.

What Is a Tempo Run?

A tempo run, also called a threshold run, is a sustained effort at a single pace held continuously for a defined period, typically 20 to 40 minutes for recreational runners.

The target pace is your lactate threshold pace, which most runners experience as comfortably hard. It is the pace you could sustain for approximately an hour of racing, faster than a comfortable long run but slower than a race effort. A useful real-world test: at tempo pace you can speak in short broken phrases but would not want to hold a conversation. If you can talk easily you are running too slowly. If you cannot speak at all you are running too hard.

A standard tempo session looks like this: 10 to 15 minutes of easy warm-up jogging, 20 to 30 minutes at threshold pace, 10 minutes of easy cool-down. The middle section is held at a consistent, controlled effort the entire time. There is no variation in pace, no recovery jogs, no surges. The challenge is sustaining the pace as fatigue builds toward the end.

What Is a Fartlek?

A fartlek is a continuous run that alternates between faster and slower paces, with the transitions governed by feel rather than a fixed schedule. Unlike the tempo run, which holds a single sustained pace, fartlek moves through multiple effort levels in the same session.

A typical fartlek session looks like this: 10 minutes of easy jogging to warm up, then a series of surges at a hard effort with easy recovery jogs between them, continued for 20 to 35 minutes, followed by 10 minutes of easy cool-down. The duration of each surge and each recovery is self-selected. You might run hard to the next corner, jog until you recover, then surge again up the hill. Or you might run hard for one minute, jog for two, and repeat. The method is flexible and effort-based throughout.

The Core Difference

The single clearest distinction between a fartlek and a tempo run is continuity of effort.

A tempo run demands sustained, continuous effort at one pace for an extended period. This is its defining feature and the source of most of its benefits. You hold the pace when it becomes uncomfortable. You do not back off. You do not take a recovery jog halfway through.

A fartlek involves intentional variation. The harder surges are harder than tempo pace. The recovery phases are easier than tempo pace. The session moves across a wide range of intensities rather than sitting at one.

Everything else follows from this distinction.

What Tempo Runs Do Better

Tempo runs are most useful when the goal is sustained, controlled performance at a demanding pace. Their steady structure makes them especially effective for runners who need precision rather than variation.

Sustained Pace Development

The tempo run’s primary benefit is teaching your body and mind to sustain a specific fast pace under accumulating fatigue. This is a skill that has to be practiced. No other workout replicates the experience of holding a hard, controlled effort for 20 to 30 continuous minutes quite as directly.

For runners targeting a 10K, half marathon or marathon, the ability to hold goal race pace under fatigue is fundamental. Tempo runs build this capacity specifically.

Lactate Threshold Precision

Tempo runs are the most direct method for raising your lactate threshold because they hold you at or slightly above that threshold for an extended continuous period. The sustained nature of the effort is the key. Your body adapts to clearing lactic acid at a higher rate when it is required to do so continuously, not intermittently.

Fartlek surges also stress the lactate system, but the recovery jogs between surges allow partial lactate clearance that a tempo run does not permit. For pure threshold development, tempo runs are the more targeted tool.

Pacing Discipline

Running a proper tempo requires genuine pacing discipline. The most common mistake is starting too fast, feeling comfortable for the first ten minutes, and then struggling badly in the final third. Learning to pace a tempo correctly, starting conservatively and finishing strong, is a transferable skill that improves race execution directly.

What Fartlek Does Better

Fartlek shines in areas where flexibility, responsiveness, and range matter more than perfect pace control. Its changing rhythm gives it strengths that a steady tempo run does not have.

Multi-system Training

Fartlek trains aerobic and anaerobic systems simultaneously within a single session. The surges push you above threshold into anaerobic territory. The easy recovery phases develop aerobic capacity. The transitions between the two train your body to handle rapid intensity shifts.

Tempo runs work primarily at the aerobic-anaerobic boundary. They do not develop the anaerobic system meaningfully because the pace never rises above threshold for extended periods.

Race Simulation

Real races at every distance involve pace variation. Competitors surge. Hills change the effort level. The middle miles of a 10K rarely feel like the tempo runs you trained with. Fartlek trains the physiological and psychological response to unpredictable pace changes in a way that a steady tempo run cannot.

Flexibility and Error Tolerance

On a day when your legs feel flat, a tempo run is brutal. You have a pace target to hit and the session either succeeds or fails. A fartlek on the same day self-regulates. You still run hard efforts, but the hard efforts will naturally be slightly shorter and slightly slower, the recoveries slightly longer, and the session still produces a useful training stimulus.

This flexibility also makes fartlek significantly more appropriate for the base-building phase of training, when fitness is lower and running at threshold pace for 20 to 30 minutes is genuinely difficult or not yet possible.

Beginner Accessibility

For runners who have not yet built the fitness or pacing awareness to execute a proper tempo run, fartlek provides a comparable cardiovascular stimulus without the requirement to hold a specific pace. You cannot really run a bad fartlek, which makes it an ideal introduction to quality speed training.

A Side-by-Side Comparison

If you want the difference in the simplest possible terms, this is what each workout emphasizes.

Effort Type

• Tempo run: single sustained effort at one pace
• Fartlek: variable effort alternating between hard surges and easy recovery

Structure

• Tempo run: precisely structured, defined pace and duration
• Fartlek: loosely structured or unstructured, governed by feel

Recovery during workout

• Tempo run: none, the effort is continuous throughout
• Fartlek: active recovery jogs between surges

Primary system trained

• Tempo run: lactate threshold, aerobic endurance at sustained pace
• Fartlek: aerobic and anaerobic systems simultaneously

Best phase of training

• Tempo run: race-specific preparation, peak fitness
• Fartlek: base building, early season, recovery weeks

Best for

• Tempo run: half marathon and marathon runners, pacing development
• Fartlek: beginners, trail runners, all phases of training

Mental demand

• Tempo run: high, requires discipline to hold pace under fatigue

• Fartlek: moderate, self-regulating, lower cognitive load

Error tolerance

• Tempo run: low, a bad day significantly impacts session quality

• Fartlek: high, adapts naturally to daily fitness variation

The Seasonal Argument

Many experienced coaches organize their training around a seasonal progression that moves from fartlek to tempo to intervals as the competitive season approaches.

In the base-building phase, fartlek is the primary quality workout. Runners develop aerobic fitness, build the habit of running at faster efforts, and accumulate training without the precision demands of threshold or interval work. This phase typically lasts eight to twelve weeks.

As the training plan moves into a race-preparation phase, tempo runs become more prominent. The runner has the fitness to hold threshold pace for meaningful durations and needs to develop the specific ability to sustain that pace under race fatigue.

In the final weeks before competition, structured track intervals targeting race pace are often added alongside or in place of tempo runs.

Fartlek is never fully removed from a good training program. Many coaches reintroduce it as a recovery week substitute for tempo runs or intervals, keeping quality sessions on the schedule without the precise physiological demands of threshold or VO2 max work.

When to Choose Fartlek

Fartlek is usually the better choice when flexibility, feel, and adaptability matter more than hitting an exact threshold pace. Choose fartlek if:

• You are new to speed training and want to start building faster efforts without a pace target.
• You are in the base-building phase of your training cycle.
• Your legs feel flat or you are coming back from a minor illness and want a quality session that adjusts to your current state.
• You run on trails where maintaining a consistent pace is impractical.
• You have been doing weekly tempo runs for several months and want a mental break from the structure.
• You are a masters runner and want a speed stimulus with lower joint stress than track intervals or road tempo sessions.

When to Choose a Tempo Run

A tempo run makes more sense when your training needs a steady, measurable effort that directly supports race pacing and threshold development.

• You are 8 to 16 weeks out from a goal race at half marathon distance or longer.
• You want to develop your ability to sustain goal race pace under fatigue.
• You need measurable data to track whether your threshold fitness is improving.
• Your coach has prescribed tempo work as part of a structured training plan.
• You are specifically trying to raise your lactate threshold in the most direct and time-efficient way.

The Honest Answer to Which One You Should Do

Both.

If you are currently doing neither, start with fartlek. It is more accessible, more forgiving and produces broad fitness benefits that prepare you for the precision demands of tempo work.

If you are already doing fartlek regularly and approaching a goal race, add tempo runs to your schedule as a second quality workout per week.

If you are an experienced runner with a coach and a structured training plan, you are probably already doing both in the appropriate phases. The question becomes how to weight them at each point in the year, and the seasonal progression described above provides a sensible framework.

The runners who improve most consistently are rarely the ones who found the single best workout and repeated it forever. They are the ones who understood what different methods do and rotated between them deliberately.