Fartlek Runs: What They Are and How to Do Them

Fartlek runs are a versatile, adaptable, and even fun workout. Any runner can incorporate them into their training. They are also highly effective, no matter how your level of experience or your running goals.

What Are Fartlek Runs?

The word “fartlek” is borrowed from Swedish and means “speed play.” In the first half 20th century, Scandanavians dominated the running scene and attributed their success to the use of “speed play” workouts in training. Now, fartlek runs have been adopted by the larger running community as a versatile type of speedwork and alternative to track workouts.  

Fartlek runs can be structured or unstructured. They use effort, not pace, as a guide. More often than not, fartleks are performed on the roads or trails, not a track. 

Simply put, a fartlek is a type of interval workout – a very versatile interval workout. You alternate between faster repetitions and slower recoveries. Exactly how fast and how slow depends on the purpose of the workout.

The Benefits of Fartlek Runs

Because of their versatility, fartleks are a valuable workout any runner or season. They can be used by both beginner and experienced runners, for base-building and race specific training, for trail and road runners, and everything from the 5K to the ultra marathon. 

Fartlek workouts teach you how to calibrate your internal GPS. Whether the effort is vaguely prescribed (noticeably faster) or more precise (5K race effort), your perceived effort is still the primary parameter. Pace is an external metric that can be affected by terrain, weather, fatigue, or stress. Fartlek runs require you to learn how to monitor your effort, both controlling yourself and pushing yourself. 

Finally, fartlek workouts reduce your injury risk. The reasoning is two-fold: they encourage variety without overreaching. Variety, including a variety of paces, reduces your risk of overuse injury. For that reason, fartleks are beneficial even if your goal is not to run faster. For type-A runners, the emphasis on effort prevents pushing inappropriately hard just to hit a certain pace.

How to Use Fartlek Workouts in Your Training

How you structure and utilize a fartlek run depends on your current training phase. Every run should have a purpose; the phase of training, your current fitness, and your goals inform that purpose. 

During the base building season, fartleks can add variety without detracting from the overall intention of the training block. The focus is on running noticeably faster as feels good, without any pace goals. Typically, the effort is not as intense as during race training. The work intervals will be shorter and the recovery intervals longer. 

In a race training cycle, you can scale a fartlek to increase the stimulus. This can be done either through increasing intensity or volume. (Experienced runners can increase both.) Instead of focusing on simply running faster, the hard intervals will have a prescribed effort – 5K race effort, very hard, etc. This is often a harder effort than you would run during the base building season. The recovery intervals will shorten, which also increases the intensity of the workout. You can increase the volume by running more intervals and/or lengthening the duration. 

Like any high intensity running workout, fartleks should only constitute a small percentage of your training load. Do a fartlek run every 1-2 weeks, depending on your training structure, fitness, and goals. 

Structured vs. Unstructured Fartlek Workouts

Unstructured fartleks are truly based on feel. You not only determine the effort level based on how you feel, but also the duration of both the hard and easy intervals. You can use landmarks such as city blocks, hills, or loops around a park. Additionally, you can also add an element of structure to unstructured fartleks; for example, set the time, but leave the recovery unstructured so that you run easy until you feel recovered. 

Structured fartleks use a set duration of time for both the work and recovery intervals. However, these workouts still rely on effort as the main parameter. Even if you have a pace goal, the main purpose should be focusing on effort. 

You can use a structured fartlek as a substitute for a track workout. For example, if you had 6 x 800m at an 8:00 minute mile pace with 400m recovery jogs, you could instead run 6 x 4 minutes at 5K race effort with 2.5-minute recovery jogs. 

Scaling a Fartlek Workout

You can scale multiple parameters of a workout to change its intended effect. These parameters include intensity, duration of work interval, and duration of the rest interval. 

Let’s take the example of a tried-and-true fartlek run: 1-minute intervals. 

Scale the intensity: 

The intensity of the hard intervals affects the purpose of the workout. You can scale it depending on your goals and where you are in the season. Typically, the closer you are to a race, the more intense the workout. There are exceptions, such as doing a speed segment before marathon training or a race-week workout. 

 For example, early in a training cycle or during a base-building period, you might just run the 1-min intervals at a noticeably faster effort (exactly how much faster is based on how you feel) to simply reintroduce faster running. Closer to a race, you would run them at a very hard effort to develop leg speed. You can also vary the intensity within the workout itself, by starting slower and progressively running faster throughout the workout (such as with this fartlek workout).  

Scale the rest interval:

The longer the rest, the less intense the workout. If it’s early in the season or if you are new to speedwork, you might opt for longer rest intervals. Later in the season, the work intervals shorten within reason (you still need appropriate recovery, especially if working at or near VO2max), You can also scale the intensity of the recovery interval: make it a very slow recovery jog for high-intensity work intervals, or your normal easy pace if the work intervals are less strenuous. 

In the example of a 1-minute fartlek, you could lengthen the easy intervals to 1.5-2 minutes. If you are focusing on developing leg speed and VO2max, you would keep the rest relatively short at 1-minute in duration. 

Scale the number of intervals:

The more repeats, the harder a workout is. Beginner runners will complete fewer intervals, as will more experienced runners during base building. The more fit you are and the closer you are to your race, the more repeats you do. 

Intensity also determines the number of intervals. For example, if you are running the repeats at a very hard intensity, you will complete fewer. If you are running them closer to lactate threshold, you complete a higher volume.  

In the example of 1-minute fartleks, novice runners may complete 6-8 repeats. Intermediate and advanced runners may do 10 intervals during a base-building workout and then progress to 12-15 intervals during peak weeks of training. 

Beyond the Roads: Fartleks on Trails

Trails rarely feature clear mile markers and GPS signals can be spotty in wooded or remote areas. Anything requiring precise distance of pace becomes trickier on the trails. Fartleks are the ideal speed workout for off-road running. Any time-based fartlek works perfectly on the trails, especially if you adjust your effort for changing terrain. 

Sample Fartlek Runs

• Hilly fartlek: I commonly prescribe this workout during base building or to trail and ultra runners. It’s simple and adaptable yet effective. After an appropriate warm-up (10 to 30 minutes, depending on the duration of the run and your overall weekly mileage), you run hard on the uphills, steady on the flats, and recover on the downhills. You can also adapt it if you are training for a descent-heavy trail race: hard on the uphills, steady on the downhills, recover on the flats, or even hard on the downhills, steady on the uphills, recover on the flats. 

• Fartlek long run: This is not a beginner workout. Incorporating a fartlek into a long run is best reserved for experienced marathoners and half marathoners who have adapted to the distance. The variations are endless. Typically, you run the hard interval at half marathon to marathon pace with a longer recovery interval at normal easy pace. An example would be 2 minutes at half marathon pace, with 4-8 minutes at easy pace. Depending on your level of fitness, you repeat this over the course of five to seven miles in the middle of a long run. 

• VO2max fartlek: This is the one with which most of my athletes have a love-hate relationship. Research indicates that 3 to 5 minutes is a sweet spot for developing VO2max. Three-minute repeats are mentally and physically demanding, yet appropriate for various points in training. After a 10-20 minute warm-up, run 4-6 x 3 minutes hard (3K-5K effort) with a 2 to 3-minute recovery jog (depending on the point in training and your fitness). Pace does not matter as much as effort; you should be working enough that you can only speak a word or two at a time.

• Leg speed fartlek: Often the simplest workouts are the most effective. 1-minute intervals seem simple, yet it is a fantastic workout for 5K runners to ultra runners. The intervals develop leg speed and improve fast-twitch muscle recruitment. Whether you are looking to crank out a fast 5K PR or maintain your pace at the end of a 50K, these repeats should be part of your training plan at some point.

More Fartlek Workouts:
Long and Short Fartlek
Countdown Fartlek Workout
Fartlek Workouts for the 5K through Marathon
Marathon Fartlek Workout

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Linking up with Coaches‘ Corner! 

Do you use fartlek runs in your training?
Do you prefer structure or an element of freedom in your workouts?