Key takeaways
Yasso 800s are 10 × 800 m where your 800 time in minutes and seconds matches your goal marathon time in hours and minutes
The rule comes from Bart Yasso's own experience and a Runner's World article, not from a published study
In the VDOT model the Yasso time roughly equals 800 m at your 5k race pace, so the session tests speed more than marathon endurance
Yasso 800s may be the most famous marathon workout ever named after a person. The rule is simple: run 10 × 800 m, and your average 800 time in minutes and seconds predicts your marathon in hours and minutes. Run 3:30 reps, run a 3:30 marathon. It is memorable and a good session. It is also only a rough predictor, and nobody has studied it.
Where Yasso 800s come from
The workout is named after Bart Yasso, a long-time Runner's World staffer later known as its Chief Running Officer. Amby Burfoot, a Boston Marathon winner and Runner's World editor, wrote about the session after Yasso told him he had been doing it for years before his marathons and that it matched his finish times. In his 2001 piece "The Real History of the Yasso 800s", Burfoot recalled talking to about 100 runners of widely differing abilities and finding that the rule held up.
That is the whole evidence base: one runner's experience and an editor's informal survey. A search of PubMed finds no study testing Yasso 800s. That doesn't make the workout useless; it means the prediction is folklore.
Yasso 800 workout: how to run it
- Warm-up: 15 minutes easy and a few strides.
- Reps: 800 m (two laps of a 400 m track) at your target time. Even pacing; the last rep should be as fast as the first.
- Recovery: jog for the same time as the rep.
- Build-up: start with 4 to 5 reps about 8 to 10 weeks out and add one a week, reaching 10 reps roughly two to three weeks before the race. Don't add a rep until you hit your times.
- Cool-down: 10 minutes easy.
One session a week at most, in place of your usual interval day. More ideas in VO2max workouts.
Yasso 800 rest time
The version Burfoot described uses a jog recovery equal to the rep time: 3:30 reps, 3:30 jogging. A popular alternative is a 400 m jog, which works out similar for most runners. Standing rest makes the session easier and the prediction even more optimistic. Shorter recovery makes it harder and arguably more marathon-like, but it is no longer the classic session, so don't compare times.
Yasso 800 calculator
The first two columns are the Yasso rule. The others are what the Daniels and Gilbert VDOT model (used in our VO2max running calculator) says a runner of that marathon fitness should run. They are model estimates, not measured data.
| Goal marathon | Yasso 800 time | Model VDOT | Model 5k | Model half | 800 m at model 5k pace |
|---|---|---|---|---|---|
| 3:00 | 3:00 | about 54 | 18:48 | 1:26:16 | 3:01 |
| 3:15 | 3:15 | about 49 | 20:24 | 1:33:40 | 3:16 |
| 3:30 | 3:30 | about 45 | 22:00 | 1:41:06 | 3:31 |
| 3:45 | 3:45 | about 41 | 23:36 | 1:48:35 | 3:47 |
| 4:00 | 4:00 | about 38 | 25:14 | 1:56:06 | 4:02 |
| 4:30 | 4:30 | about 33 | 28:30 | 2:11:14 | 4:34 |
| 5:00 | 5:00 | about 29 | 31:49 | 2:26:28 | 5:05 |
Why Yasso 800s are only a rough predictor
Look at the last column. Across the range, the Yasso time lands within a few seconds of 800 m at the runner's model 5k race pace. In other words, Yasso 800s ask you to run ten reps at about 5k pace with generous recovery. That is a fine VO2max-type session, but it measures your speed and aerobic power, not the things that decide a marathon:
- Fractional utilisation and economy. Marathon pace is set by how much of your VO2max you can hold for hours (VO2max vs lactate threshold).
- Endurance and fuelling. A runner can nail 10 × 800 m on 30 km a week and still fade badly after 30 km on race day.
- Speed bias. Runners with a strong middle-distance background can run fast 800s and get an optimistic prediction; high-mileage, slow-twitch runners may find it pessimistic.
So treat a good Yasso session as "your speed is in place for this goal", not "you will run this time". For a more honest forecast, plug a recent half marathon into the calculator, and check your long runs and weekly volume. The marathon training and VO2max guide explains why a given VO2max can support a wide range of marathon times.
Yasso 800 for half marathon
No half marathon version of the rule has been published. Some runners adapt it, but there is no consistent formula and nothing to validate one against. Instead:
- Run Yasso-style 800s as your VO2max session in the middle weeks of a half marathon block.
- Predict the half from a recent 5k or 10k with the VDOT model (the "Model half" column above shows the link).
- Use lactate threshold training as the main specific work, since half marathon pace sits close to threshold for most runners.
Where Yasso 800s fit in a plan
Use them in the build phase, stop the last full session about two to three weeks out, then taper. Set effort with the heart rate zone calculator: by the later reps you should be near the top of zone 4 or in zone 5. Keep the rest of the week mostly easy, whether you go by the 80/20 rule or a heart-rate cap such as the MAF training method. For shorter races, the intervals in the 5k training plan are a closer fit.
Safety: this is general information, not medical advice. Ten fast reps are a hard session; build up gradually, and stop and seek medical advice if you get chest pain, unusual breathlessness or dizziness.
Frequently asked questions
What is a Yasso 800 workout?
Ten repeats of 800 m, each run in the same minutes and seconds as your goal marathon time in hours and minutes, with a jog of the same duration between reps. A 3:45 marathon goal means 800 m in 3:45.
How accurate are Yasso 800s?
There is no published research testing them. They tend to work for runners who also do the long runs and mileage a marathon needs, and to flatter faster, speed-oriented runners. A recent half marathon is a better predictor.
How long is the rest in Yasso 800s?
The usual version uses a jog recovery that lasts as long as the rep, so 3:30 reps get 3:30 of jogging. Many runners use a 400 m jog instead, which is similar for most paces.
Can you use Yasso 800s for a half marathon?
There is no established half marathon version of the rule. You can still run the session as VO2max work, but predict your half from a recent 5k or 10k with a race calculator instead.
Sources
- Burfoot A. The Real History of the Yasso 800s. Runner's World, 2001 (as cited by Wikipedia: Bart Yasso)
- InsideHook. Do "Yasso 800s" actually predict your marathon time? insidehook.com (origin, recovery equal to rep time, Burfoot's 100-runner quote)
- Joyner MJ, Coyle EF. Endurance exercise performance: the physiology of champions. J Physiol, 2008. PubMed
- Daniels J. Daniels' Running Formula. Human Kinetics (VDOT equations used for the calculator table).