I tend to do HIIT runs, meaning sprinting for X seconds then jogging for Y seconds and repeating Z times.

I've come across a discipline called Fartlek that seems to achieve the same thing. How does Fartlek vary from HIIT?

1 Answer 1


The difference is structure. Interval training is structured in either time or distance when to run hard and when to rest. Fartlek training goes based on feeling which makes it far less rigid.

You can see the comparison at the Fartlek wikipedia page. Fartlek is described as:

the interplay between the effort (exercise) and recovery (relief) are not systematically manipulated; instead, the athlete and coach determine the interplay "based on 'how it feels'" during the training.

And further down there is a direct comparison with interval training:

Intervals “are short, intense efforts followed by equal or slightly longer recovery time." By the end of a short burst of speed, the runner is barely able to keep up that pace. Unlike fartleks, interval runs are much more structured; usually running the fast and slow spurts at exact times or distances. Interval runs and tempo runs differ in the fact that tempo runs maintain a slightly fast pace for a set amount of time, while interval runs consist of alternating between sprints and slow sections instead of keeping one speed.

There can be other forms of Fartlek although maybe they don't fit the technical definition. For example, one style of training I did was I would only sprint when going uphill. This would make the intervals very random and interspersed depending on the route I took. Another would be to do random sprints between point A to point B. For example, sprint between this lamp post and a fire hydrant I see down the road. It's the randomness that makes it unstructured.

I'm not aware of any studies that determine whether intervals or fartlek style training is better. I would argue that fartlek requires more discipline from the runner to ensure that they're pushing themselves to the levels that are needed for progress. On the other hand, it would also be safer as it doesn't really encourage runner to push well beyond what they are capable of handling. The style of training one would choose depends on the individual.

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