Tag Archives: Yasso 800’s

Can the 5K help predict a marathon time in lieu of Yasso 800’s?

Recently I floated the value of using an 8K as a marathon time predictor shortly before your marathon, in lieu of the popular Yasso 800’s workout.

While the 8K/10 can cut out a middleman and give you the same result as the Yasso’s, possibly more accurate since the breaks are removed… as I mentioned, it can be difficult to find an 8K to race.

I’ve done some more research based on Daniels’ pace recommendations, and I realize that a 5K may provide a similar prediction. This may work better for most people, because 5K races are a lot more common and easier to find, register for and complete.

Of course, the following assumes:

  • You’re trained to run the marathon distance, and can comfortably run at least 2.5 uninterrupted hours.
  • Your workouts haven’t been a substantial struggle to complete (aside from finding the time to do them, and making the proper effort to recover from those workouts)
  • It also helps if you know your goal pace, though this is not necessary.

Basically, you simply run a 5K at your best sustainable effort for the 5K distance. Do not taper for this 5K, and do not plan for rest days afterward. This is not going to be a max effort 5K.

If you know your marathon goal time, a starting guideline is to aim to run the 5K about one minute per mile faster than your marathon goal pace. It doesn’t have to be exactly this, but if unsure how fast to run the 5K this is a fine starting point. And if that seems too fast for you… your marathon goal time might be too ambitious for a full 26.2, even if you’ve been able to hit it during marathon-pace workouts.

Either way, the best effort guideline for this race: Run the 5K as if you have to also do a regular workout tomorrow. You don’t want to take it too easy, but you don’t want to exhaust the tank to try and PR.

Running the 5K by feel honestly will produce the most accurate result. Run at a steady pace you can hold for 3 straight miles, and avoid the instinct to finish hard and kick at the end.

If at any point in the 5K you feel you can go faster, you may increase your pace just a little bit. But don’t exhaust yourself before the finish.

The harder the 5K is to run, the less likely you can hold for 26.2 the marathon pace it will predict. Your aerobic fitness is part of what’s being estimated, so it’s important this 5K be a challenging but otherwise aerobically comfortable effort.

Run the 5K. Once you have your 5K finish time, it’s time for some math.

Step One: Take your total time in raw minutes: Take the seconds, divide them by 60, and add that decimal to the whole number minutes.

For example, let’s say an aspiring marathoner who run 50 miles a week and has knocked out his/her 20 miler… subsequently ran the 5K in 24:24.

24 seconds is equal to 0.4 minutes, which added to 24 whole minutes makes 24.4.


24 seconds / 60 = 0.4 minutes

24 minutes + 0.4 minutes = 24.4 minutes.

Step Two: Now, multiply that number by 0.16.

24.4 x 0.16 = 3.90

This number is the number of estimated hours it should take you to finish the marathon.

Step Three: You can take the decimal in this hours estimate, and multiply that by 60 to display the number of minutes.

0.90 hours / 60 = 54 minutes

3.90 hours —-> 3 hours, 54 minutes

5K Marathon Prediction: 3 hours, 54 minutes

According to the 5K prediction, a trained marathoner who can knock out a 5K in 24:24 can likely run their marathon in 3 hours, 54 minutes.

If the above hypothetical marathoner were to run the Yasso 800’s, they likely could complete their 800 reps in an average of 3 minutes 54 seconds.

If they ran the 8K/10, it would take them roughly 39 minutes on the dot.

But the 5K can give them the same estimate, in a fraction of the time and effort. The only extra effort is in doing the math.

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The Yasso 800’s marathon predictor workout: An idea for a simple (and not so simple) improvement on the workout

The Yasso 800’s are a classic marathon predictor workout, where the average/median/whatever of your ten 800 meter reps should correspond to your likely marathon time, e.g. averaging 3:45 per rep indicates you’ll run the marathon in 3 hours 45 minutes. (I’ve previously written some tips and thoughts on handling the workout.)

The workout’s accuracy can depend on a lot of things…

  • How easy the reps are
  • How much rest you’re taking between reps
  • How closely your reps are to your average rep time, whether all your reps are the same or if they’re all over the place
  • Whether you hold steady throughout the workout or get slower as it progresses
  • And of course how adequately trained you are to run the marathon distance

Of course, it’s a bit crude as a predictor. From common sense, how can a series of 800 meter repeats predict how you will run for 42,195 uninterrupted meters, 3-4 weeks later? The workout doesn’t match the race in any way. You certainly won’t run the 800’s at the same pace you plan to run the marathon (BTW if you did, and manage to match your prediction at the marathon… then you certainly could have run the marathon faster). You will likely run the Yasso 800’s at something close to 5K pace, while your marathon pace will be closer to a sustained moderate effort.

But let’s be real: It’s very difficult to predict how your training has prepared you to run your upcoming marathon. There’s no real adequate predictor workout for the distance, because the distance itself is beyond most human capabilities. You can easily run the distance of a 5K in a workout. You can’t reasonably run a 26 mile workout unless it’s a long run, and few will run that far in their longest runs. It’s very hard to do.

Bart Yasso‘s workout is a somewhat reliable approximation of what runners can do. It’s based on his vast experience, and how the relative effort in the 800’s indicates the corresponding pace at which you can run a marathon when adequately trained. His workout came about from finding a clear correlation that proved largely true for most trained marathoners who successfully attempted the workout. It does match up for many, even when for various reasons it doesn’t match up for others.

I think there’s a better, more accurate form of this predictor workout. But it requires more discipline and is of course more difficult… even though the format is a lot simpler:

  • Run an 8K with your best even-paced effort.
  • Divide the time by 10.

That’s the marathon prediction.

The premise: The Yasso 800 workout consists of 10 reps of 800 meters. 10 multiplied by 800 is 8000 meters, aka the exact distance of an 8K.

The key difference in this 8K workout is that you’re removing all of the rest breaks, and running every inch in one uninterrupted go.

The hard part of course is that maintaining a steady pace in an 8K becomes a lot harder. It’s important that, like running a good workout rep, you don’t necessarily race the 8K as you normally would. You focus on maintaining a steady effort that at the finish line you could theoretically continue running for a few more miles.

In effect, it’s like an 8K run at 10K pace. Or, to brutally simplify it, it’s one 8000 meter rep at 10K pace.

The Yassos are broken into 10 more easily manageable reps. It’s a lot easier to maintain your pace for 3-5 minute bursts than to figure out and hold a suitable pace for 30-50 minutes. You have to know how fast you intend to go, start at that pace, and then ensure you hold it until you cross the finish.

But you’re already planning to do that at the marathon, right? Ideally (though many best laid plans get laid to waste on a marathon race day), your plan is to run at your chosen pace for all 26.2 miles. If you can hold a pace for 26.2 miles, why should a slightly faster pace over 4.971 miles be all that tough?


I realize 8K pace is substantially tougher than marathon pace, and that’s one reason I suggest running an 8K test at something closer to 10K pace… along with bearing in mind that you may have a tune-up coming up or having just passed, and that you are after all in the final phase of training for a marathon. You don’t want to kill yourself trying to run a baller 8K that’s not your goal race.

I realize a key element to the Yassos is that you get to stop and rest, minimizing the strain of running those 8000 meters at a fast pace. I realize that if you run an 8K, you’re possibly going to run a slower pace than you ideally would for Yasso’s, which typically can be done at 5K pace.

But here’s the key, stated as a rhetorical question: Wouldn’t that make an 8K time divided by 10 a more accurate prediction? Many say that Yassos tend to predict about 5-10 minutes fast. Many say the Yasso prediction tends to be too optimistic. If you are forced to maintain a slightly slower pace for 5 straight miles… won’t that offer a more possible prediction for your race?

Also, even though it’s not a race specific workout to run an 8K at 8K pace… neither is running 10 reps of 800 meters at 5K-10K pace. What does that have to do with finding and sustaining marathon pace? At least an 8K’s uninterrupted effort is more specific to what you need to do in a marathon (run somewhat hard, without stopping).

And in the Yasso’s, with those shorter reps, it falls into the same trap as most interval speedwork: It’s easy to outrun the workout, and run the reps harder than you would run in a longer race. Give yourself enough rest, or take in enough energy, and you could race 10 really good reps that aren’t at all indicative of what you could do in a 5K, let alone predict how you’d run the marathon.

It’s no wonder so many people find Yasso 800 predictions fast.

I would recommend trying an 8K Divided By 10 (8K/10) test in lieu of Yasso 800’s. In fact, I wish I had thought to do it in past training cycles. I definitely will do it next time.

If you’re doing speedwork, an 8K/10 can replace a speed session for that week, which would still allow you to do a tune-up half marathon the week before or after if desired.

8K races are not easy to find, I realize, like 5K’s, 10K’s and Half Marathons. While reasonably popular, it’s a somewhat odd distance. They come and they go.

Those in Chicago running a spring marathon (like Boston!) could use the Shamrock Shuffle for this. Barring that, a late August or early September 8K could work for the peak fall marathon season (some Illinois towns outside of Chicagoland do offer late September 8K’s).

Outside of that, scour Running In The USA and see if any are available nearby within 3-5 weeks of your goal race. If not, I challenge the RAM Racings of the world to put one up if there isn’t one available in a given area.

Of course, the easiest way to make an 8K test happen is the hardest one to find the discipline to do: Map out 5 miles, and run it out yourself… or go find a full size track and knock out 20 laps in one go. I’ll be frank: If you have the discipline to train for and run a marathon, you should be able to find the discipline to make yourself run an 8K on your own at 10Kish pace. If that’s what it takes and you want to try this, I have faith in you.

No matter how you do it if you dare… run at 8K, divide your finish time by 10, and that’s probably as good a prediction of your marathon time as any Yasso 800’s workout could give you.

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