Runners typically love structure. For the most part, we follow our training plans to a tee, nail each pace and distance, and take recovery as serious as we take each workout. But structured training isn’t the only way to get a good workout in and improve your long-term performance.
Yep, that unstructured run concept is called a fartlek. If you’re wondering what exactly a fartlek run is, you’re not alone. The Swedish for “speed play” can be confusing, but we’re here to break it all down for you. We chatted with a few experts to find out more about what fartleks are, how they’re different from other speed workouts, why you should add them into your training, and how exactly to run them.
What Is a Fartlek Run?
Fartlek is literally, playing around with speeds—essentially, it’s a form of unstructured speedwork. Unlike tempo and interval work, fartlek is completely unstructured—which means you can ditch the running watch if you want to—and alternates moderate to hard efforts with easy throughout.
For example, after a warm-up, you play with speed by running at faster efforts for short periods of time (to a designated tree or sign) followed by easy-effort running to recover, says Chicago-based running coach Jenny Hadfield.
The premise is that you speed up for a period, then you ease back to your normal easy pace for a period, adds Janet Hamilton, C.S.C.S., owner of Running Strong in Atlanta, who uses fartleks to “test the waters” with some shorter speedwork—and if an athlete can successfully complete them for a few weeks in a row with no injuries or excessive soreness, they will feel more confident moving into more structured track- or road-based speedwork.
“Some people do these with time as the measurement,” she says. “For example, one minute at a faster effort, then three minutes at an easy effort. Others do it with distance as the measurement—run faster for a quarter of a mile, recover easy for a half mile. The nice thing about a fartlek is that there is no one set distance or time, it’s variable.”
It’s fun to be able to mix up the pace and time. And in doing so, you reap the mental benefits of being pushed through an unpredictable workout.
The goal, Hadfield says, is to keep it free-flowing so you’re untethered to the watch or a plan, and to run at harder efforts but not a specific pace. Fartleks give you a stress-free workout that improves mind-body awareness, mental strength, and stamina.
What Differentiates Fartleks From Other Speed Workouts?
While fartleks should be pretty unstructured for the most part, tempo and interval workouts are more disciplined.
“Tempo workouts are like an Oreo cookie, with the warmup and cooldown as the cookie, and a run at an effort at or slightly above your anaerobic threshold—the place where your body shifts to using more glycogen for energy—as the filling,” Hadfield says.
Tempo runs should be done at an effort that’s just outside your comfort zone—you can hear your breathing, but you're not gasping for air. If you can talk easily, you’re not in the tempo zone, and if you can’t talk at all, you’re above the zone, Hadfield says.
Intervals are short, intense efforts followed by equal or slightly longer recovery time, Hadfield says. A good example of an interval workout would be: run at a hard effort for two minutes after your warmup, then run at an easy effort for two or three minutes to catch your breath.
“You’re running above your red line and at an effort where you are reaching hard for air and counting the seconds until you can stop—a controlled fast effort followed by a truly easy jog,” Hadfield says.
Why Should You Incorporate Fartleks into Your Training?
“Fartleks allow the body to gradually adjust to harder training without being forced to stick to a particular pace or distance,” Alan Culpepper, a two-time U.S. Olympian and running coach previously told Runner’s World. “The heart works harder, as do the specific running muscles, but because you’re in control, it allows for an easier adaptation.”
Hamilton agrees, adding that they’re a great way to introduce faster or more intense running into your routine when you’ve been focusing on building your base at easy efforts.
“I like doing them in the transition from a base phase into a sharpening phase, and I usually start with a couple of weeks of this unstructured speedplay before shifting into more disciplined, structured intervals either at the track or on the roads,” she says. “I tell my athletes that if they did the workout correctly, they should feel invigorated at the end of it, not exhausted.”
How to Incorporate Fartleks Into Your Training
Adding fartleks to your regular routine will boost your overall fitness whether you’re training for a race or just looking to stay in good running shape. Your cardiovascular system, stamina, and efficiency will improve.
“For beginners, the biggest benefit in doing them is not locking into a single pace,” Alan Versaw, a 14-time state champion coach at The Classical Academy in Colorado Springs, Colorado, previously told Runner’s World.
Hamilton says she usually starts out with a routine where the athlete warms up for at least a mile, then shifts into fartlek mode.
And, while fartleks don’t necessarily have to have a ton of structure to them, Hamilton says she likes to give her athletes some guidance, “mostly because they have a tendency to beat themselves up by going too fast and too long, and doing too many if they’re left to their own devices.”
However, she adds, it’s fine to just play with them and do “landmark fartleks,” running faster to the next stop sign or light pole, then recovering easy, or running faster for four mail boxes and then recovering for four mail boxes.
A common fartlek workout Hamilton prescribes is running at what feels like a 10K effort for a minute or two, then recovering at a normal, easy effort for three minutes.
“I tell [my athletes] that this should feel fun, not terribly taxing— sort of like you’re ‘loosening the reins’ on a frisky race horse and letting him or her play a little. Keep it fun, keep it light. If you feel taxed at the end of that one- to two-minute interval, you probably pushed harder than I intended you to.”
There is no “right” way to run fartleks (that’s the beauty of them!), but there are a few guidelines Hamilton follows.
“I usually only prescribe them once a week, and I usually don’t prescribe them until an athlete is running consistently at a mileage base that will support the higher intensity,” she says. “Someone who wants to do a four-mile run that incorporates fartleks in it should probably be running at least 20 miles a week consistently with no injuries.”
It’s also worth noting that including fartleks isn’t a wise idea if you’re currently battling an injury or just coming back from one, according to Hamilton. She recommends getting healthy first, then reintroducing speedwork.
More structured fartleks can also come in handy if you have a training goal in mind. Culpepper recommends the following weekly workouts:
5K or 10K Training Fartlek
- Warm-up easy
- 8 to 12 x 1 minute hard with 1 minute easy
- 6 to 8 x 2 minutes moderately hard with 2 minutes easy
- Cool-down easy
Descending Ladder Fartlek
- Warm-up easy
- Start at a 10K pace for 6 minutes. Increase speed slightly for 5 minutes, then 4 minutes, 3 minutes, 2 minutes, and 1 minute. You should end the final minute at 5K pace.
- Cool down easy
Half or Full Marathon Fartlek
- 4 to 8 x 3 minutes moderately hard with 2 minutes easy
- 3 x 5 to 8 minutes comfortably hard with a 2-minute jog between each
- 2 x 10 to 13 minutes at half-marathon effort with a 2-minute jog between each