1 Fartlek Definition That Makes Sense

A fartlek definition that actually makes sense is not easily simplified into a dictionary’s explanation.  It’s a not so common term from Sweden, that even many Swedes have never heard, that translates into English as “speed play”.

Run faster during specified intervals.  Run slower between the faster intervals.  But, for most runners and athletes, they rarely think of the word ‘play’.  

Fartlek Definition - Kids playing

We understand speed yet most fartlek definitions exclude the word play.  It’s application and connotation are more like pure interval training. Maybe something like our track coach would assign everyone whilst training on a trail.

‘Play’ means lots of things to each person, but for the majority of us, I would venture it means to have fun or make a game of it.  Almost any kind of running is fun for me. I just love running. But, I would not say that I am playing a game when I am running on a typical distance training session.  That is why the fartlek is so cool. It incorporates little games that any of us can make up in order to engage our fast twitch muscles and better prepare us for races.

I think the original meaning of the word fartlek involved making “speed play” a game.  

Farlek Definition – A Speed Game

Fartlek Definition - Cycling

A game like ones we made up when we were outside playing with our friends.

I like to think of a fartlek as being defined as a “speed game”.  This does not mean race. It’s a game that you can play by oneself or with a group.

The other missed opportunity in the typical definition of fartlek training is its application in other sports.  Fartleks can also be used for swimming, cycling, rowing, or almost any other sport. I love doing fartleks while training on my road bike.  I want to start incorporating fartleks into my swim training as well. The point I’m trying to get at is that you can create ‘speed games’ and use them in almost any sport discipline.  

Why Should I Do Fartleks?

Fartlek Definition - Stadium Running

Now that we have put a better definition on the word fartlek, why is it a good idea to do them? Simply put, it is to train our fast twitch muscles. Fast twitch muscles are what I like to call ‘power and speed muscles’.  They kick-in when you need a burst of speed or power, or when your slow-twitch muscles have been exhausted.

There are loads of new sport science related studies that are being done on this interplay of muscles during athletic activities everyday.  There is a ton of research and scientific data that supports what I am writing here, so I am trying to distill it to terms that most of us can relate to.  

When you perform a fartlek workout you are training your body to respond using slow-twitch/ endurance muscles and 2 types of fast-twitch muscles/ power and speed muscles.  The slower pace works the endurance muscles and the faster pace works your power and speed muscles.

The goal is to get your body to respond to stressors during a race more efficiently.  During endurance races, such as a triathlon, you have to speed up a hill on the run or bike.  You have to speed up during a section of the swim to get past a few other people. These power and speed moments allow your fast twitch muscles to do what they are designed to do.  And after you have met that demand, your body needs to get back into using its slow-twitch muscles. The similarity of fartleks and racing are quite apparent.

How Do I Do a Fartlek?

Fartlek Definition - Running

I have written a few articles to help give you a starting point to create your own fartleks.

What is a fartlek?

Fartlek training

Beginner Fartlek Training Schedule

Being an triathlete, I try to do 1 day of fartlek training for each discipline.  I run, swim, and bike twice a week. So 1 of the 2 days is designated for fartlek training.  But, as most of us are looking for fartlek training for running, I would recommend sticking to a simple plan.  Here is a plan I designed for a half-marathon distance race. The fartleks being used are a simple ‘timed-fartlek’ and a ‘park/trail – fartlek’


20 minute warm up at moderate pace

15 minutes fartlek ( 1 minute at moderate pace, 30 seconds at 80%, repeat)

10 minute cool down


Calisthenics/ Weight training


60% effort distance run (45 – 120 minutes)


Calisthenics/ Weight training

20 minute 40% effort


Fartlek Definition - Tree to Tree Running

20 minute warm up

20 minute Tree to Tree Fartlek Run (use trees on a trail to give 90% efforts in short bursts.  Slow down to 20% effort between fartleks)

10 minute cool down


30 – 90 minute 50% effort


Rest Day

I hope this article has helped you understand a little more about how I think a fartlek definition should be explained, and why fartleks are so important.  

4 thoughts on “1 Fartlek Definition That Makes Sense”

    • Thank you so much!!! It’s very encouraging to see these kinds of comments. It definitely helps put a smile on my face… I hope you have a wonderful weekend!

Comments are closed.