In running-speak, there’s a good F-word: Fartlek.

Attributed to a Swedish cross country coach from the 1930s and roughly translated, it means “speed play.” When pro runner and coach Corrine Malcom prescribes fartleks for her athletes, that’s exactly the effect she’s asking for. “I always liked how ‘speed play’ sounded, in particular that it embodies what I want athletes to feel during the work out—play,” she says.

In its purest form, a fartlek is designed by the runner, by feel, or even on a whim based on landmarks like telephone poles. But many coaches employ fartleks as a training tool for specific end-goals. As the coaching legend Arthur Lydiard wrote in Running With Lydiard, the fartlek “incorporates aerobic and anaerobic running, usually according to the condition and capabilities of the runner on the day. Stride out here, sprint there, jog somewhere else, spring up a hill and so on.”

Physiologically, fartleks foster both speed and endurance by increasing pace and requiring continuous running. Athletes, then, learn to change gears, adapt for faster recovery, and run more efficiently with good form to boot.

But the perks of fartleks aren’t just physical. They’re practical and mental, too. Most importantly, though, they’re fun. Time- and effort-based workouts take weight off an athlete’s shoulders. Without pressure to hit specific or expected paces, an athlete can focus on practicing patience, sharpening racing skills and letting progression come naturally.

David Roche, co-founder of Some Work All Play (and my own coach), prescribes fartlek-format workouts for many of his athletes. “The main reason is psychological. I don’t want athletes to think they are their splits. That story can be fun as it unfolds when an athlete is improving over time, but it often will take a turn for the worse when things aren’t going perfectly,” he says. “Limiting the opportunities for self-judgment based on watch feedback can help some athletes love themselves no matter how fast their intervals were.”

Throughout the year, fartleks can be tailored to promote preparation, recovery or anaerobic capacity. That’s the beauty of them; they’re versatile. Like other coaches, I adapt them to varied terrain, weather conditions, fitness, season and/or time constraints for the athletes I work with.

For example, with the fall racing season at hand, road runners can use this workout style to hone their speed and ability to surge to match moves. Trail runners, on the other hand, might use a flexible approach on race-specific terrain (think: hills) to improve overall fitness and confidence simultaneously. But even those among us who don’t have a target race on the calendar can glean benefits from fartlek’ing.

With that in mind, here are three fresh fartlek workouts to try now:

For Road Runners

Preparing for peak performance, whether you’re training for a big, hairy goal or key race, requires the ability to respond to what’s happening around you. Oh, and to keep up. This fartlek is designed to increase your speed, ability to sustain it and practice surging—in particular when you’re feeling tired.

*Warm up at an easy pace for 10 to 20 minutes
*4 to 6 strides with jog back recovery
*2x 2 minutes fast (think 5k-10k effort), 2 minutes easy
*4x 1 minute fast, 1 minute easy
*4x 30 seconds faster, 30 seconds easy
*Cool down at an easy pace for 10 to 20 minutes

For Trail Runners

At some point during a trail or ultrarace, the course (or day) is going to throw you a curveball. To knock it out of the park, practice varying your intensity based on terrain. The goal is to feel confident (or at least competent) no matter the challenging pitch (pun intended). This workout targets your high-end aerobic capacity, too.

*Warm up at an easy pace for 10 to 20 minutes
*On a 4- to 8-mile (depending on your current mileage and training) hilly, undulating trail:

*Run moderate to hard on uphills
*Run easy on the downhills
*Run steady on flats

*Cool down at an easy pace for 10 minutes
*Run 4 to 6 strides with full recovery

For Rebounding and/or Rebuilding Runners

Whether you’re transitioning into a more competitive training cycle, returning from an injury, or just picking up the pace after downtime, this long-run workout—used by Roche, Malcom and other coaches—will help your body and mind prepare for quality workouts down the road by refocusing your form, without a lot of stress. Aim to complete at least a few weeks of training with strides (1 to 2 times a week) on top of easy mileage before you jump into faster workouts.

This is also a great workout to implement while cross training on the bike, elliptical or in the pool; it’ll break up any monotony and provide an additional aerobic benefit.

*Warm up at an easy pace for 15 to 20 minutes
*Every 5 minutes, surge for 20 to 60 seconds (at a moderate to faster pace)
*Repeat 8 to 12 times for 40 to 60+ minutes, depending on the length of your run
*Cool down at an easy pace for 15 to 20 minutes