Fartlek, which is Swedish for Speed Play, is an effective and fun way to incorporate some speed work into your training. A Fartlek workout consists of a series speed-recovery intervals of various lengths, but what makes it unique is the runner will not know the length of the interval. Runners will need to pace themselves in order to make it through the entire workout.
After a warm-up the runner will run a speed interval followed by a recovery of equal length. The length of an interval will vary in length 30 second to 3:30 minutes. Intervals will vary in length from :30 to 3:30Fartlek Yourself