Fartlek, which means “speed play” in Swedish, is an unstructured form of physical training in which you literally play with the speed and intensity of a workout. While the term is most typically associated with treadmills and long distance running, it is a technique that can also be applied to any type of continuous cardio exercise, including rowing and step machines.
By alternating the “intensity of your workouts, you will burn more calories than you would by keeping a steady pace. While running, the runner’s body first burns the stored sugars and then begins to burn fat after the sugar is depleted. During a fartlek workout while the body is trying to replace the sugar storage, “fat stores are burned in a metabolic effect that lasts long after your workout. Fartleks are a great option for people that run for their health because the fat burning portion makes it a very efficient exercise.
Fartleks keep runners’ bodies at top shape so that they can keep racing. Putting fartlek runs in a workout routine keeps “muscles, tendons, nerves, etc. used in running going at top capacity. In other words, regularly implementing fartleks keeps your body strong enough to maintain the mechanics of racing.
Three speeds version
In order to add more variety, runners can add another speed into the run. Within any run, “there is no reason why three different paces should not be included. This would change a normal fartlek by doing a jog, run, and a full out sprint.
Many runners use music while they run. Runners can use their music as a template for their fartlek run by changing their speed according to different parts of a song. For example, they can speed up during the chorus and slow down for the rest of the song.