–noun a training technique, used esp. among runners, consisting of bursts of intense effort loosely alternating with less strenuous activity.
1950–55; < Sw fart speed + lek play (dictionary.com)
You have to love the word Fartlek. Fartlek is a fun word for “Speed Play”. This is an out of the box way to do sprints. It allows the runner to escape the structure of a training plan and play with their speed throughout a training run.
Fartleks are incredibly beneficial for endurance training in helping to build speed and strength. Runners should have a good running base before trying Fartleks. Attempting these and other sprints before the body has adapted to running can cause injury, so please be careful. For those that have run for a while or completed a race this is a great way to train, once a week, to get closer to a PR (personal record).
With Fartleks you choose the pace and duration. One example of a training run would be to run 10 – 15 minutes or 1 mile to warm up. During the second mile you would incorporate the fatrleks. The easiest way to do this is to find objects on your route that you can measure, such as light poles. You can sprint from light pole to light pole and then easy run or walk to the next. For more advance you can sprint the distance of 2 light poles and then slow your pace for one. Increase as you improve your endurance. You can also do this with street blocks, mailboxes or any other object, just have fun with it. Another way is to just run, challenging yourself to run faster till you fill anaerobic (almost breathless) then slow your pace till you recover then do it again. Challenge yourself and enjoy it! Then run the third mile or final 10 – 15 minutes at an easy pace to cool down.
To make this more structured you can do it with time. For a beginner, try sprinting 30 seconds and then an easy pace for 2-5 minutes. As you train and this gets easier then you can run the sprint for 1 min or longer and then recover for 2-5minutes. The best part about this form of training is being able to easily adjust it to your ability and to how you feel on that particular day. You can also increase from a one mile distance to one and a half and then to two miles, etc.
This type of training needs to be done on one of the shorter weekly runs not on the weekly long run. Fartleks are also a great pre training season session, allowing you to build strength before the long runs begin. Trying to do this too often or for too long can cause injury. Listen to your body and have fun!
Below is a video on fartleks, tempo runs and hill training. All three are beneficial to distance running.