What Yasso 800s are and where the rule comes from
The rule fits in one line: your marathon goal in hours:minutes becomes your 800 m repeat time in minutes:seconds. A 3:30 marathon goal means 10 x 800 m in 3:30 each, which is 1:45 per 400 m lap, with a 3:30 easy jog between repeats.
The workout is named after Bart Yasso, then race services manager at Runner's World. He described it to editor Amby Burfoot at the Portland Marathon, saying he had been doing it for about 15 years. Burfoot wrote it up in the 1990s and named it "Yasso 800s". His check was informal: he "talked to about 100 runners", from a 2:09 marathoner to several over 4 hours, and published no timing data.
The original prescription, as Burfoot wrote it:
- Once a week, starting a couple of months before your marathon.
- Build from 4 to 10: 4 repeats in the first week, then one more each week until you reach 10, which takes 7 weeks.
- Equal-time recovery: jog for as long as each repeat took.
- Finish early: the last session "at least 10 days before your marathon, and 14 to 17 days would probably be better."
Why the rule works, and why it usually flatters you
In short: running your Yasso times shows you have the speed for your marathon goal. It does not show you have the endurance, which is why the prediction tends to be optimistic.
It is fixed arithmetic. Whatever your goal, Yasso pace is 1.14 times your marathon speed (48 divided by 42.195). For a 3:00 goal, each 800 m is about 25 seconds faster than marathon pace (3:00 against 3:25); for a 4:00 goal, about 33 seconds faster (4:00 against 4:33).
It lands on your 5K race pace. By Jack Daniels' VDOT formula (VDOT is a single fitness score worked out from a race result), Yasso pace is almost exactly the 5K race pace of a runner who can run your marathon goal: 3:45/km against 3:46/km for a 3:00 goal, 5:00/km against 5:03/km for a 4:00 goal. Ten solid repeats say your 5K fitness matches the goal.
It does not test endurance. Ten repeats with full jog breaks add up to 8 km of fast running in pieces; the marathon is 42.2 km without a break. Burfoot himself told readers to do "your normal marathon training, paying special attention to weekend long runs." The research on speed-based predictions points the same way:
- Vickers and Vertosick (2016, 2,303 recreational runners) found the Riegel formula, which projects marathon time from shorter races, gave times at least 10 minutes too fast for half of the runners. That study tested Riegel, not Yasso; we cite it because Yasso also projects from speed.
- Tanda and Knechtle (2013, 126 runners) found weekly training distance predicted marathon time alongside training pace.
- We have not found any published study that tests the Yasso rule itself. Yasso later called it a "coincidence, correlation" he noticed in his own training.
Is Yasso pace a threshold workout? The numbers say no
Some articles, including the current Runner's World page on the workout, describe the effort as close to threshold pace. Threshold pace is roughly the fastest pace you could hold for about an hour in a race. Our calculation with Daniels' formula disagrees: across goals from 2:40 to 6:00, Yasso pace is 16-27 s/km faster than threshold pace and close to 5K race pace.
| Marathon goal | Yasso pace | 5K race pace (same fitness) | Threshold pace | Marathon pace |
|---|---|---|---|---|
| 3:00 | 3:45/km | 3:46/km | 4:01/km | 4:16/km |
| 3:30 | 4:23/km | 4:24/km | 4:40/km | 4:59/km |
| 4:00 | 5:00/km | 5:03/km | 5:19/km | 5:41/km |
| 5:00 | 6:15/km | 6:22/km | 6:38/km | 7:07/km |
Yasso pace sits just slower than the pace at which you reach your maximum oxygen uptake (vVO2max, the top of Daniels' interval pace range). Coach Mario Fraioli, checking it with Daniels' VDOT calculator, likewise found that the workout "actually works out to around your 5K pace". If you want a true threshold session, get your paces from the training pace calculator.
How to run Yasso 800s well
Use the session as a weekly speed check inside normal marathon training, not as the plan itself. You can load it into the interval timer so each repeat and jog is called for you.
- Build gradually. Start at 4 repeats and add one per week up to 10. If fast running is new to you, stay at 4-6 repeats for a couple of weeks before adding more.
- Choose your recovery on purpose. An equal-time jog is the original rule. A 400 m jog is how Bart Yasso describes his own version. A shorter 90-second to 2-minute recovery makes a harder, stricter test, but it is a variation, not the original.
- Run every repeat at the same time. Ten even repeats tell you more than nine slow ones and a sprint. If you fade in the second half, set a slower goal next week.
- Cap the effort for slower goals. From about a 4:20 goal onward, Yasso pace is 4 s/km or more faster than the 5K race pace that matches the goal: by Daniels' formula about 4 s/km faster at 4:30, 7 s/km at 5:00 and 13 s/km at 6:00. In that range, run fewer repeats and treat your 5K race pace as the ceiling.
- Keep the long run and the mileage. Reaching 10 repeats confirms speed for your goal; it does not guarantee the marathon. The weekly long run and total volume carry the endurance side.