> Runners who purposely alternate between fast and slow while training areparticipating in which kind of exercise?And the answer: fartlek.Coming from the Swedish word that means "speed play," a fartlek is when therunner changes between fast sprints and easy jogs, all in the same run. The goalis to mix things up and keep training from getting too boring.Photo credit: Shutterstock.Oftentimes, doing your run training at the same pacewill result in a performance plateau. Interestingly, the key seems to lie ineasy running, rather than intense repetitions of timed trials. Fartlek trainingis a form of exercise that incorporates variety and freestyle into the moreuniversally practiced interval training. In fartlek training, runners will change their pace based on naturalenvironment. Most fartlek runners will begin their workout without a strict orspecific plan for their run, and will base their relative speed on landmarksaround them. For example, beginners in fartlek training are recommended to picka nearby landmark (say, a building or lamp post), and run at their faster 5kpace until reaching that point. Then, the runner can drop to a slower,sustainable pace more akin to that of a marathon. This can continue for as longas desired, though beginner fartlek sessions should be at least 40 minutes toallow for proper warm up and cool down. Fartlek training can also be done with music as well. Some runners chooseslower, more relaxed songs that allow them to slow their pace, followed by moreupbeat songs to help inspire a 5k pace.To learn more about fartlek training and its benefits, check out the videobelow.