The world is a blur when you run this fast. Photo: Kako, Flickr

Fartlek means "speed play" in Swedish and yes, it's pronounced just the way you think it is. Go ahead! Get your giggles out, then consider the serious boost you can give your training by adding fartleks into your regular running routine.

Developed in the 1930s, fartleks are an excellent way for both beginners and advanced runners to improve speed and stamina. Unlike traditional speed workouts, fartleks add short bursts of speed into your "normal" run. When the burst is over, you return to your normal cruising speed until you're recovered and start the cycle over again.

"This kind of training is a great way to keep your body guessing," says Lisa Bender, a trainer at CrossFit Central. "Fartleks push you outside of your comfort zone and help you become more efficient."

And fartleks come with a built-in "no excuses" policy because they can be added into just about any running routine and can be done on any terrain. It can be as simple as telling yourself to "run fast to that next telephone poll" or as precise as sprinting for 20 seconds at the one-minute mark.

Carey Kepler, owner of CrossFit Central, recommends doing fartleks on a track for an accessible, fun way to get started. "Use the straight-aways for the 'fast' part of the interval and the curves for recovery that allows you to catch your breath but doesn't let you completely 'cool down.'" Runner's World also offers two fartlek workouts to help you get started.

If you're wondering if fartleks are right for you, Kepler has the answer. "Fartleks add intensity," she says, "and we all could use a little of that in our lives."

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