How to run Yasso 800s
- 1
Warm up
10 to 15 minutes of easy running, then a few relaxed strides. - 2
10 × 800 m at your rep time
Two laps of a track each. The first few should feel quick but controlled and the last few hard, about how a 10K race feels. - 3
Jog for as long as each rep took
A 3:30 rep gets a 3:30 slow jog. Do not stand still. - 4
Cool down
10 minutes of easy jogging.
If ten is too many, start with fewer and add a rep or two each time over the following weeks. A first set of four to six is a sensible test. Run them in the last two months before a marathon, not in race week.
Where the rule comes from
Bart Yasso, a long-time Runner's World staff member, used the session for years to judge his own marathon fitness. His colleague Amby Burfoot wrote it up for Runner's World and gave it the name (Burfoot, Runner's World, 2001). The workout layout above, with equal-time jogs and the 10K feel, is as coach Greg McMillan describes it.
It was never tested in a study. It is a rule of thumb that held up well for the runners Yasso and Burfoot knew.
How far to trust the prediction
The rule is a straight line: every minute on your 800s is an hour on your marathon. Race times do not scale like that. Jack Daniels' VDOT model, which sets every pace in a Run-R plan, slows more gently as distance goes up. The table puts the two side by side for the same runner.
| Marathon | Yasso 800 | 800 at I pace | VDOT | Yasso rep predicts |
|---|---|---|---|---|
| 2:30:00 | 2:30 | 2:29 | 66.3 | 2:30:50 |
| 2:45:00 | 2:45 | 2:43 | 59.3 | 2:46:46 |
| 3:00:00 | 3:00 | 2:57 | 53.5 | 3:02:40 |
| 3:15:00 | 3:15 | 3:12 | 48.7 | 3:18:30 |
| 3:30:00 | 3:30 | 3:26 | 44.6 | 3:34:15 |
| 3:45:00 | 3:45 | 3:40 | 41.0 | 3:49:56 |
| 4:00:00 | 4:00 | 3:55 | 37.9 | 4:05:33 |
| 4:15:00 | 4:15 | 4:09 | 35.2 | 4:21:05 |
| 4:30:00 | 4:30 | 4:24 | 32.8 | 4:36:32 |
| 5:00:00 | 5:00 | 4:53 | 28.7 | 5:07:12 |
| 5:30:00 | 5:30 | 5:22 | 25.4 | 5:37:35 |
Two things stand out. For fast marathoners the two agree. For slower ones Yasso asks for quicker reps than interval pace: about -8 s per rep at 5:30. Read the other way, hitting your Yasso times points to a marathon slower than Yasso says: about a minute at 2:30, 6 minutes at 4:00 and 8 minutes at 5:30. McMillan makes a similar point from coaching: runners with more speed than endurance tend to run a few minutes slower than their Yasso time.
Both numbers assume the endurance work is done. 800 m reps test speed, not whether you can hold a pace for three or four hours, fuel well and pace the first half. A good long run block matters more than any one session.
Yasso 800s in a Run-R plan
Run-R plans do not schedule Yasso 800s by name. Marathon plans use intervals at I pace instead, from 5 × 1000 m up to 4 × 1600 m, plus marathon pace runs, which are a more direct test of race pace. If you like Yassos as a check, swap one interval session for them in the last eight weeks and keep the rest of the week as planned.
For your race-day splits, see the marathon pace chart. To predict from any race, use the race time predictor.