800m Repeat Timer
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Yasso 800s, popularised by Bart Yasso, are 800m repeats run with a recovery jog of the same duration as the repeat itself. The session builds from a handful of repeats toward ten, and it is best known for a prediction: run your 800s in the same minutes and seconds as your goal marathon time in hours and minutes[1].
Equal-time recovery is what makes the session distinctive. It is more generous than most VO2max interval prescriptions, which keeps the repeats fast and repeatable rather than turning the later ones into a survival exercise — the point is to hold the same pace ten times, not to fade progressively.
The prediction, and what it ignores
Ten 800s at 3:30 predicting a 3:30 marathon is a memorable rule and a rough one. It says nothing about weekly mileage, long run length, fuelling or heat — all of which decide marathons more reliably than 800m speed does.
A runner with the speed and without the volume will hit the 800s and not the marathon. The session is better used as a fitness marker you repeat across a block than as a forecast you plan a race around.
Build the count, not the pace
The productive progression is more repeats at the same pace rather than faster repeats. Starting at five or six and adding one per session toward ten gives a session that gets harder in the way marathon training should — through accumulated volume at intensity.
Running the first three faster than target is the common error, and it makes the last three impossible. Consistency across the set is the whole signal.
Recovery is equal time, not equal distance
Jog for the same duration as the repeat took, not for a fixed 400m. A slower runner therefore gets more recovery in absolute terms, which is deliberate — the ratio is what makes the session repeatable across abilities.
Keep the recovery jogging rather than walking where you can. It keeps the legs turning over and makes the transition back to pace less abrupt.
The prediction is Yasso's rule of thumb, not a physiological model[1]. It assumes marathon-appropriate training volume, which it does not measure.
| 800m repeat | Predicted marathon | Recovery jog |
|---|---|---|
| 2:45 | 2:45 | 2:45 |
| 3:00 | 3:00 | 3:00 |
| 3:15 | 3:15 | 3:15 |
| 3:30 | 3:30 | 3:30 |
| 4:00 | 4:00 | 4:00 |
| 4:30 | 4:30 | 4:30 |
| 5:00 | 5:00 | 5:00 |
- The prediction ignores weekly mileage, long run length, fuelling and heat — all of which decide marathons more than 800m speed.
- Progress by adding repeats toward ten, not by running them faster.
Source: Yasso 800s — training session and marathon prediction rule popularised by Bart Yasso, Runner's World
Sources
- Yasso 800s — training session and marathon prediction rule popularised by Bart Yasso, Runner's World , Widely documented in running literature — accessed 2026-07-28