Training with the magic predictor of your marathon time: Yasso 800s

Training with the magic predictor of your marathon time: Yasso 800s

Our co-author of the book The Power to Run (expected March 2022) Koen de Jong uses the Yasso 800s method for his marathon training and asked us if we knew the method and could calculate the required power to run the Yasso intervals. We answered in the affirmative to both questions and in this article we explain the method.

What is the Yasso 800s?

The Yasso 800s was created by Bart Yasso, the Chief Running Officer of the American magazine Runner’s World. Bart Yasso has been inducted into the Running USA Hall of Champions and is referred to in America as the ‘Mayor of Running’. He has raced on all 7 continents and has won the U.S. Duathlon Championship in 1987.

His method is very simple and consists of running a number of intervals over 800 meters. The trick is that you have to make sure that your time over the 800 meters (in minutes and seconds) is equal to your marathon goal time (in hours and minutes). So if you run (or want to run) a marathon in 3 hours you have to run the 800 meters in 3 minutes. How simple can it be?

The structure of the workout is also very simple:

  • Warm-up for 10 minutes (gentle jogging, exercises and possibly some 100 meter strides to get used to the speed)
  • 800 meter interval at the converted pace (so 3 minutes for a marathon time of 3 hours)
  • Recovery during the same time as the interval (so 3 minutes in the example)
  • Repetitions: in the beginning 3 or 4 times, expand to finally 10 times
  • Cooling down for 5 or 10 minutes, including exercises/stretching.

And voilà, you’re done!

Bart Yasso recommends doing this workout 1 time a week. The method is very popular and also successful. It is recommended to do the other parts of a full marathon training during the rest of the week, especially the long endurance runs, the recovery runs and the pace training.

What power should you use for the Yasso 800s?

In the table below we have worked out some examples.
The first column shows the (desired) marathon time.
In the second column we have determined the corresponding marathon power with the formula: Watts/kg = speed in m/s*1.04. In a previous article we showed that this gives a very good approach for most runners.
The third column shows the time for the Yasso 800s in minutes and seconds, which as mentioned equals the marathon time in hours and minutes.
In the fourth column, the required power for the 800 meters is calculated (with the same formula).
In the fifth column we have finally calculated how much extra power you have to use during the 800 meters compared to your marathon power. This always turns out to be 13.76% with this method.

Critical analysis of the Yasso 800s

At first glance, this method seems too simple to be true. You would think: how is it possible to base a marathon time on intervals over 800 meters and vice versa?

Still, there’s something in it. Of course, you run slower as the distance increases. In our books we have shown that for most people the speed decreases by 5% when the distance doubles. Now of course there are people with a particularly good endurance, but when you cannot run an 800 meter interval in 3 minutes you can forget about running a marathon in 3 hours. No matter how good your stamina is! That there is a more or less fixed relationship between the 800 meters and the marathon time is therefore not entirely surprising, although this will not be exactly the same for everyone.

At its core, the Yasso 800s is ‘just’ an interval workout where the pace of the intervals is not determined by your trainer, but by your desired marathon time. In another previous article, we explained that interval training is an important building block to become a better runner. With the Yasso 800s, the pace of your intervals is therefore adjusted to your level, in this case by the marathon goal time you can or want to run. If you don’t reach that level, you’ll have to adjust the pace of your workouts and the expectations for the marathon….

Intervals make you a better runner

Many performance-oriented runners train at least once a week at their club on the athletics track. Traditionally, your trainer often bases the schedules for interval training on your 10K race time. On another day in the week, some longer intervals, accelerations or hills in the workout on the road or in the forest are on the program.

The reason is that with intervals you can train at high intensity. It improves your base speed. The goal can also be to train your various energy systems (you have four!) or to get your body used to lactate acid. Because recovery is built in between intervals, these types of training are less stressful as a race.

800 meter intervals at 109%?

In our earlier article, we gave the table below for the required power as a function of the distance of the intervals. For intervals of 800 meters, we indicated that you have to run it at 109% of your FTP (the power that you can maintain for 1 hour).

The fact that you see the percentages increase quite a bit at short interval distances is caused by the fact that your anaerobic energy systems provide extra energy there. Your anaerobic fuel supply is very limited. You can therefore only keep these high powers and speeds up for a short time.

What about the Yasso 800s? Do you also run it on 109% of your FTP? We have calculated that for the examples, see the table below. The first 2 columns are the same as in the first table, but in the third column we have calculated the FTP that is equivalent to the marathon time. In the fourth column we have finally calculated the required power for the 800s as a percentage of your FTP. Because your marathon power is relatively lower compared to your FTP at slower marathon times, you see that the percentage with which you have to run the 800 meters slowly decreases.

The result of these calculations is that the top runners with the Yasso method have to train almost at 109% of their FTP, but that for slower runners the percentage drops to order 103%. The training is therefore less stressful for them, especially since the recovery time at Yasso is rather long (after all, as long as the interval itself, so 4 minutes if you run a marathon in 4 minutes).

Our conclusion is that the Yasso 800s is a great method to determine the pace for your intervals on your individual level, based on your marathon time. For slower runners, the pace seems to be a bit too slow and the recovery time is also a bit too long. However, it does seem a bit dubious to us to calculate your marathon time based on your Yasso 800s interval times. Keep in mind that in the marathon you may ‘hit the wall’ and your stamina may be better or less than average.

Our book ‘The Secret of Running’ is for sale in our webshop. Also available in German as ‘Das Geheimnis des Laufens’, and in Italian as ‘Manuale completo della corsa’