Run intervals – “Kenyan fartlek”

6-8x 1:00 @ 5k pace / 1:00 float
4x 2:00 @ 5-10k pace / 1:00 float
2x 3:00 @ 10k pace / 1:00 float

5k pace. If you don’t (most likely) have an actual 10k time, you can add +10-15 sec to your 3k time trial pace (per km). For example: 12:00 3k = 4:00/km + 0:10-0:15 (for adjustment) = estimated 4:10-4:15km/h pace.

10k pace. If you don’t (most likely) have an actual 10k time, you can add +20-30 sec to your 3k time trial pace (per km). For example: 12:00 3k = 4:00/km + 0:20-0:30 (for adjustment) = estimated 4:20-4:30km/h pace.

“Float” pace. The Float is a steady effort ( 0:30-0:45/km slower than your “Hard” pace) rather than a slow recovery jog. The first 10 seconds of the transition to float is hard, aim to keep your cadence. If your float pace starts to drop, you’re pushing the “hard” segments too much (back-off a little).

Overview.
The “Kenyan Fartlek” replaces passive rest with a steady float, forcing your body to clear lactate while maintaining a “respectable” pace. The challenge is not only to keep the intended paces on the “hard” segments but also during these floats.

Effort.
Hard segments: 8–9/10 effort. These range from 5k pace (1:00s) down to 10k (3:00s).
Float segments: 6/10 effort. This is a “Moderate” steady run, roughly 30-45 seconds per km slower than your hard pace. Never walk or stop.

Feel.
The transitions are the trick of this session. You will feel your heart rate and breathing go up during the hard efforts, but the real work happens in the first 15 seconds of the float as you fight the urge to slow down to a jog. You should feel “recovered enough” to start the next rep, but never fully fresh.

Adaptation.
Improve your lactate shuttling (the ability to recycle metabolic byproducts as fuel while running at a high aerobic output). Build running toughness and specific “speed endurance” by teaching the legs to keep turning over under cumulative fatigue.

Debrief. Take 2–3 minutes after the workout to reflect
– Did you maintain a steady float without dropping to a slow jog or walk?
– Did you successfully step down your pace as the intervals got longer (e.g., 5k pace for the 1:00s vs. 10k pace for the 3:00s)?
– How did your posture hold up during the final 3:00 segments when the fatigue was highest?
– Did you overcook the 1:00 sprints, making the following floats impossible to manage?
– What adjustment would help you stay more consistent next time?