If you’ve resolved to get more fit in 2025, you’re in luck because almost any exercise will steer you toward that goal. But of all your options, few are as effective, simple, adaptable, and enjoyably impertinent to brag about as fartleks.
Fartleks are an informal version of interval training. To start, head outside, warm up for a few minutes with whatever activity you most enjoy—whether it’s walking, running, biking, unicycling, or snowshoeing—and then pick a landmark a short distance ahead. It could be a tree, a colorful mailbox, or an unusual rock formation.
Speed up your pace until you reach that landmark, then drop back to your original pace, letting your heart rate and breathing slow as you look for another marker. Vary the distance to these goals, and aim for perhaps 30 minutes of fartleks once a week to start.
Fartleks are one of the most unthreatening ways to sprinkle intensity into our activities. A growing body of science indicates that intensity, even in small amounts, can benefit workouts—not just for our strength and endurance, but for our health and longevity too.
“Fartlek training is quite a good way to improve fitness,” said Ulrik Wisloff, head of the cardiac exercise research group at the Norwegian University of Science and Technology in Trondheim. “I do it, and I recommend it to people who say they don’t like exercise, because it’s never boring.”
What’s the Meaning of ‘Fartlek’?
For generations, competitive athletes used highly structured, intense interval training—usually on a track or treadmill—to increase their speed and endurance. This kind of training is potent; it makes you faster but is also grueling, demanding expertise and planning, and is rarely anyone’s idea of a rollicking good time.
This is where fartleks come in. Fartlek translates to something like ‘speed play’ in Swedish, a term usually attributed to the Swedish Olympic decathlete and running coach Gosta Holman, who reportedly developed the concept in the 1930s after the Swedish cross-country team were repeatedly trounced by their neighbors, the Finns, during international competitions.
The Link Between Intense Exercise and Longevity
Fartlek training is more than entertaining, though. It’s also one of the easiest ways to amplify the intensity of your preferred workout, making it even more beneficial.
But why would you want to intensify your exercise?
“You’ll see greater increases in VO2 max with relatively intense exercise,” Wisloff pointed out. VO2 max is a measure of our bodies’ ability to deliver oxygen to cells and is strongly associated with longevity. The lower someone’s VO2 max, the likelier they are to die young, and vice versa.
The importance of exercise intensity for lifespan became particularly evident in a large-scale 2024 study, during which 7,500 middle-aged and older adult men and women wore high-tech activity trackers for at least a week. Researchers calculated the intensity of their daily activities and followed them for about seven years, tracking deaths.
Interestingly, the overall intensity of people’s daily activities turned out to be a better longevity predictor than how much they moved around. Those who were the most sedentary were approximately 14 percent more likely to have died in the subsequent years than those who engaged in some physical activity. Furthermore, individuals whose physical activities were mostly low intensity were about 37 percent more likely to have died compared to those whose routines included even a little more intense exercise.
Intense Exercise Doesn’t Have to Be Hard
The notion of making your exercise more intense can seem daunting. But there’s no need to worry, said Martin Gibala, an exercise scientist at McMaster University in Ontario, Canada, who studies interval training. He emphasized that exercise intensity is a spectrum, ranging from light exertions to the all-out intervals Olympians endure.
Just incrementally boosting the intensity of your activities from casual strolls to brisk walks can substantially enhance your health and fitness, Gibala noted. Significant benefits arise when you occasionally escalate the effort of some of your sessions from “green to yellow” on a green-yellow-red effort gradient.
Alternatively, Wisloff suggested using the talk test: to find the optimal intensity for health improvement, you should be able to converse during intervals but not sing, as singing requires most of your respiratory resources.
In my experience, I incorporate fartlek training a few times a week to inject energy, variety, and delight into my standard workout routine. The term is catchy and the workout invigorating, leaving me pleasantly fatigued at the end. Fartleks, consistently varied, never become dull.
Just a few days ago, during my Christmas Eve workout, I encountered many holiday dog walkers along my route. I made each canine a marker and introduced myself. While my intervals were brief, the shared joy was contagious, making it my most enjoyable workout of 2024.
Do you have a fitness question? Email YourMove@washpost.com and we may answer your question in a future column.
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