The Kenyan Fartlek.

What is the Kenyan fartlek?

Fartlek means "speed play" in Swedish. In Iten it is played in big groups on the dirt roads, usually on Thursday, with the leader calling the changes. Because the recovery stays quick, the heart rate never drops far, so the session feels more like a hard tempo run with surges than an interval session.

How hard to run it

Segment	Effort	Feel
On	5K to 10K effort	Hard, controlled, a few words at most
Off	Steady, about marathon effort or a little slower	Moving, not jogging

The most common mistake is racing the first five "ons" and jogging the "offs". The session should feel even from the first rep to the last.

Kenyan fartlek for your level

Add two to three reps a week. Once the full version feels controlled, make the "off" a little quicker rather than adding more reps.

Where it fits in the week

In Iten, Thursday fartlek sits between Tuesday track and the Saturday long run, with easy days between. Copy that: one interval day, one fartlek, one long run, the rest easy. The whole week is in how Kenyan runners train, and more sessions are in our interval library.

Variations from Iten

• 2/1 fartlek: 2 min on, 1 min off, 10-15 reps. Closer to threshold.
• 3/1 fartlek: 3 min on, 1 min off, 8-10 reps. A marathon favourite.
• Pyramid: 1-2-3-4-3-2-1 min on, with 1 min off.
• Hill fartlek: run the "ons" on the uphills of a rolling route.

Want to run it with the groups it comes from? A running camp in Kenya runs it every week, with pacers.

Sources: traininkenya.com (training and coaching, Run the Kenyan Way: the Iten Thursday fartlek, 8 November 2026); reporting from Iten by London Marathon Events and Outside. Run Mastery is a running coach, not a medical service.