Treating your splits as a forecast
Hitting your 800s at goal pace tells you nothing certain about the marathon. The rule has never been validated, and it's often optimistic. Long runs and marathon-pace work say far more about your 26.2-mile fitness.
RunningThresholdIntermediate 97 min
Yasso 800s (10 × 800 m)
Yasso 800s: 10 × 800 m, each run in as many minutes and seconds as your marathon goal in hours and minutes, with an equal jog recovery. About 96 minutes in all. A marathon-build classic, better treated as a session rather than a forecast.
Session profile22 blocks
At a glance
- Duration
- 97 min
- Main target
- 83–87%vVO₂max4 Z4 · Threshold
- Time at target
- 38 min
- Estimated load
- 97
- Structure
- 10 × 3′46 at 83–87% vVO₂max, 3′46 recovery
- Level
- Intermediate
- Equipment
- Track (optional) · GPS watch
The session in detail
vVO₂max
Time in zone
- Z154 min
- Z25 min
- Z438 min
What the targets mean
| Target | Zone | Time | vVO₂max 14 km/h | vVO₂max 16 km/h | vVO₂max 18 km/h |
|---|---|---|---|---|---|
| 83–87% | 4Threshold | 38 min | 5:10/km–4:56/km 729–765 m per rep | 4:31/km–4:19/km 834–874 m per rep | 4:01/km–3:50/km 938–983 m per rep |
| 50–60% | 1Recovery | 34 min | 8:34/km–7:09/km 439–527 m per rep | 7:30/km–6:15/km 502–603 m per rep | 6:40/km–5:33/km 565–678 m per rep |
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What this session is for
Yasso 800s work a strong pace, between your threshold and your vVO₂max, and consistency over repeated efforts: ten times 800 metres at the same pace, with as much jogging as running. Taken as a whole, it's a big session: more than 37 minutes at a strong pace, one of the heaviest in the library.
Its fame comes from a rule: run your 800s in 3:50 and you're worth 3:50 for the marathon. Bart Yasso reportedly noticed the link in his own racing. No scientific data confirms it, and coaches often find it optimistic. Which makes sense: 800 metres says nothing about your endurance, your fuelling, or the wall at 20 miles.
Who it's for
Regular runners in a marathon build, with a few weeks of structured training behind them. The session is long and repetitive: you need to have done some interval work already. Very fast 800 m runners, or very endurance-based ones, won't get a reliable marathon pointer from it: their 800 m times are too far from their 26.2-mile profile.
When to do it
In a marathon build, one session of this kind a week is a common guideline, after an easy day or a rest day, never the day before a long run or another hard session. The first time, start with 6 to 8 reps, then build to 10 over the weeks. According to a secondary source, Yasso advises doing the last one at least 10 days before the race.
How to do it
Warm-up
15 min10′ at 60–65% vVO₂max + 5′ at 66–72% vVO₂max
10 minutes of easy running at 60–65% of vVO₂max, then 5 minutes at 66–72%. Head to a track: 800 metres is two laps, and lap splits will help you stay even.
Main set
72 min10 × 3′46 at 83–87% vVO₂max, 3′46 recovery
10 × 3 min 46 at 83–87% of your vVO₂max, with 3 min 46 of jogging at 50–60% between each. That's the default duration, about 800 metres for a vVO₂max of 15 km/h; at 16 km/h you cover 834 to 874 metres. To follow the original rule, adjust the length of the reps and recoveries to your goal: 3:30 to target 3:30, 4:00 for 4 hours. Run every rep at the same pace: the aim isn't to beat your time each week.
Cool-down
10 min10′ at 55–65% vVO₂max
10 minutes of very easy running at 55–65% of vVO₂max. Note your times: how even they are, from the first rep to the tenth, says more about your fitness than your quickest one.
How it should feel
Harder and harder as the reps go by: 6 out of 10 on the first ones, 8 out of 10 on the last, and the final three can be very hard. Running an 800 in 3:50 doesn't make you a 3:50 marathoner: there are still 25.7 miles to negotiate.
Common mistakes
Trying to beat the pace every week
Yasso 800s aren't a race against yourself. Speeding up each session to improve your 'prediction' tires you out without teaching you anything more. Stick to goal pace and finish fresh.
Finishing every rep gasping
Yasso pace sits below your vVO₂max. If you finish each 800 flat out, you're running too fast, or your goal is too ambitious for your current fitness.
Cutting the recovery
The recovery lasts as long as the effort: that's what lets you hold ten reps at the same pace. Cut it and the session becomes a different, harder and less even one.
When to skip it
Before you start
- A few weeks of structured training, including intervals.
- A realistic marathon goal, or a recently measured vVO₂max.
Skip it if
- You have pain or a recent injury.
- A long run or another hard session is planned for the next day.
Origin and evidence
Level of evidence
Limited evidenceLevel 2 of 5
A session attributed to Bart Yasso of Runner's World. The name 'Yasso 800s' was reportedly popularised by Amby Burfoot in Runner's World, in 1994 or 2001 depending on the source. Yasso is said to have noticed the link between his 800 m times and his marathons empirically. Coaches such as Jeff Gaudette (RunnersConnect) point out the lack of scientific data linking the two and a prediction that is often optimistic. Widely used, no peer-reviewed publication. Programming it by time (3 min 46) and % of vVO₂max (83–87%), the jog recovery at 50–60%, the warm-up and the cool-down are Wattson choices. Bottom line: very weak, empirical evidence.
Sources
- Burfoot A., Runner's World, « Yasso 800s »
Frequently asked questions
How does the Yasso 800s rule work?
You run each 800 in as many minutes and seconds as your marathon goal in hours and minutes: 3:30 to target 3:30, 4:00 for 4 hours. The jog recovery lasts as long as the effort. If you can hold ten reps at that pace, the rule says you're worth that time for the marathon.
Do Yasso 800s really predict marathon time?
No, not reliably. The rule comes from Bart Yasso's personal observation and has never been validated by a study. Coaches often find it optimistic: 800 metres measures neither endurance nor fuelling over 26.2 miles. Treat it as a session, not a test.
What pace should Yasso 800s be run at?
According to the rule, at your marathon goal converted into an 800 m time. In Wattson, the session defaults to 83–87% of your vVO₂max for 3 min 46; depending on the runner, Yasso pace falls between 80 and 90% of vVO₂max. Adjust the duration to your goal.
When should the last Yasso 800s session be before a marathon?
According to a secondary source, Bart Yasso advises doing the last one at least 10 days before the race. The final weeks are for tapering: keep sessions shorter, and let your legs arrive fresh on the day.
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