Fartlek, a Swedish word meaning “speed play,” is an unstructured type of speed work that can be quite spontaneous in nature. Like hill repeats, the fartlek workout is considered a transition type of workout that you incorporate into your running training program prior to beginning structured speed training. The central purpose of fartlek runs is to prepare you for the anaerobic demands that more structured speed workouts and racing provide. In short, the fartlek workout is designed to be a fun and easy way to introduce speed training into your program.
Whereas more structured speed workouts, generally done on a track or an accurately measured course, encompass specified periods and distances of fast-paced running followed by recovery periods, the fartlek workout is quite different. You can run a fartlek workout at a fast pace in varying distances and durations.
Just as you can run fartlek workouts in a variety of ways, you can perform them on various terrain, including on roads and trails. Before doing fartleks on hilly courses, however, it's best to accustom yourself to these workouts by running them on flat ground.
Fartlek Running Guidelines
Even though it is considered an unstructured workout, there are basic guidelines for fartlek running. Begin your workout with a minimum of 1–1½ miles of easy running (or a minimum of 12 minutes). End with a 1-mile cooldown, throw in speed bursts of varying times and distances, then follow each with a recovery jog.
The idea here is to practice running at a brisk effort (generally faster than your present 5K race pace), employing good running form and training your body to run anaerobically (meaning without oxygen). Push yourself until your breathing becomes labored and your pace begins to drop off. Rather than continuing to push yourself past this point (when you are running at a slow pace with deteriorating form due to fatigue), it's much more beneficial to run fast for a shorter period of time and then to resume when you recover (that is, catch your breath).
Planning a Fartlek Workout
In a fartlek workout, some runners run at a fast pace (at or faster than their current 5K race pace) to a designated landmark such as a telephone pole, then slow down to catch their breath (recover) until they reach the next telephone pole, where they pick up the pace again. They repeat this pattern of running from landmark to landmark until the conclusion of the workout.
Other runners plan their fartlek workout to be more specific. For example, after their warm-up period, they run fast for one minute followed by running a minute at an easy pace to recover. You could repeat this process through the conclusion of the workout, increasing and decreasing the duration and/or distance of fast-paced running at any time. The choice is up to you, based on your perceived level of effort and the amount of discomfort you are willing to experience.
So as not to overdo exercise and risk incurring an overuse injury, you should develop a specific plan for incorporating fartlek workouts into your training program. For example, you might want to run 30 seconds fast followed by 30 seconds easy. Then you could throw in a 45 second burst followed by a 45 second recovery job, and so forth.
The first week the novice might aim for 4 minutes of total fast-paced running (for example, 30 seconds + 30 seconds + 30 seconds + 45 seconds + 45 seconds + 30 seconds + 30 seconds), adding 2 minutes of fast effort for each of the next three weeks. By having a specific plan ahead of time for enduring a cumulation of fast periods of running, you are much less likely to become injured by overdoing your workout.