Yasso 800s: The Workout, The Calculator + The Prediction Truth

Yasso 800s are a classic speed workout that is widely used by distance runners to build endurance, pacing, and speed.

This workout has gained popularity for its simplicity and effectiveness—and for the bold claim that it can predict your marathon finishing time (we’ll dive into how accurate that is later).

Whether you’re training for your first marathon or chasing a record time, Yasso 800s can be a valuable tool to gauge your fitness and improve your race-day performance.

In this guide, we’ll break down what they are, how to do them, and whether they deserve a place in your training plan.

The Honest Truth About Yasso 800s

Bart Yasso’s 800m workout has been one of the most-shared marathon-prediction sessions in running culture for three decades. The original claim — that 10x800m at the same minutes-and-seconds as your goal marathon’s hours-and-minutes (e.g., 3:30 800s for a 3:30 marathon) predicts marathon finish time — is appealingly simple, but it doesn’t hold up tightly under research scrutiny. The session itself is still a useful training tool; just not a precise marathon predictor.

The original claim and what it actually says

Yasso’s 1994 Runner’s World article proposed running 10 reps of 800m at a target pace where the time in minutes:seconds equals the goal marathon time in hours:minutes, with equal-time recovery jogs between reps. So a runner targeting a 3:30 marathon should run each 800m in 3:30, with a 3:30 recovery jog. The session is performed once weekly during a marathon build, with reps progressively added from 4 to 10 over 10 weeks. The marathon-prediction claim was based on Yasso’s personal observation, not controlled research; it became canonical through repetition rather than empirical validation. Daniels and others have since produced more rigorous marathon-pace prediction frameworks based on lactate threshold, VO2max, and race-distance-pace tables that are more accurate but less memorable ¹Daniels J. Daniels’ Running Formula. 4th ed. Human Kinetics; 2021..

What the session actually adapts

Setting aside the prediction claim, the Yasso 800 session itself targets VO2max and high-end aerobic capacity. The pace for a typical sub-3:30 marathoner (3:30 per 800m = 7:00/mile) sits at roughly 5K-to-10K race pace, which is the classical VO2max-development zone. Billat’s interval-training literature documents that VO2max responds best to 3–5 minute repeats at 95–100 percent of VO2max, totalling 20–30 minutes of work per session ²Billat V. Interval training for performance: a scientific and empirical practice. Sports Med. 2001;31(1):13-31.. Yasso 800s are shorter than the 3–5 minute Billat recommendation but accumulate similar total time at VO2max-zone intensity, particularly for slower marathoners running 4:00–5:00 per 800m. The cumulative time-at-intensity in a full 10x800m session typically lands at 30–45 minutes, which is at or above the dose for VO2max stimulus ³Midgley AW, McNaughton LR, Wilkinson M. Is there an optimal training intensity for enhancing the maximal oxygen uptake of distance runners? Sports Med. 2006;36(2):117-32..

Why the prediction claim breaks down

The fundamental problem with the Yasso prediction is that 800m repeat performance and marathon performance are driven by different physiological systems. 800m repeats at 5K-pace are dominated by VO2max and lactate-tolerance capacity; marathon performance is dominated by lactate threshold, running economy, and substrate metabolism (glycogen storage and fat oxidation) ⁴Joyner MJ, Coyle EF. Endurance exercise performance: the physiology of champions. J Physiol. 2008;586(1):35-44.. A runner with strong VO2max but weak threshold and economy can run fast Yasso sessions and a slow marathon; a runner with the inverse profile (strong threshold and economy but average VO2max) can run slower Yasso sessions and a faster marathon than the calculator predicts. The Tanda training-volume model for marathon performance places weekly volume and long-run length as the dominant predictors, with neither reflected in the Yasso framework ⁵Tanda G. Prediction of marathon performance time on the basis of training indices. J Hum Sport Exerc. 2011;6(3):511-20.. The original Yasso article’s “evidence” was confirmation bias from a self-selecting cohort of moderately-fit runners; the prediction works in that population but fails for runners with skewed physiological profiles.

More-accurate marathon-prediction tools

The literature on marathon-pace prediction has progressed considerably since 1994. The Daniels VDOT framework uses recent race times (5K, 10K, half-marathon) plus a fitness-decay multiplier to predict marathon pace with measurably better accuracy than Yasso 800s, with typical prediction errors of 1–2 percent on real race outcomes ⁶Daniels J. Daniels’ Running Formula. 4th ed. Human Kinetics; 2021.. The Riegel formula (T2 = T1 × (D2/D1)^1.06) extrapolates from a known race time at one distance to a predicted time at another, with empirical accuracy in the 1–3 percent range for the 10K-to-marathon extrapolation ⁷Riegel PS. Athletic records and human endurance. Am Sci. 1981;69(3):285-90.. The Tanda training-volume model adds an extra layer by incorporating weekly mileage and long-run length, with reduced prediction error for runners whose training data is available ⁸Tanda G. Prediction of marathon performance time on the basis of training indices. J Hum Sport Exerc. 2011;6(3):511-20.. None of these are perfect, but each is more accurate than Yasso 800s and reflects more of the actual marathon-relevant physiology.

When Yasso 800s earn their keep anyway

The session is still useful even when treated as a VO2max workout rather than a marathon predictor. The progressive build from 4 to 10 reps over 10 weeks gives a clean track-workout structure, the goal-paced consistency teaches pacing discipline, and the 800m distance is short enough to recover from for runners with limited interval-tolerance. The Foster session-RPE work shows that perceived effort consistency across reps is one of the strongest fatigue-management markers in distance training, and Yasso’s same-pace-every-rep structure makes that consistency easy to monitor ⁹Foster C, Florhaug JA, Franklin J, et al. A new approach to monitoring exercise training. J Strength Cond Res. 2001;15(1):109-15.. The honest reading: Yasso 800s are a perfectly good VO2max session for a marathon trainee, programmed once weekly with adequate recovery, but they aren’t a precision marathon-prediction tool. Use them for the training stimulus and use Daniels VDOT or Riegel formulas for the prediction.

What Is The Yasso 800s Workout?

Yasso 800s is a workout designed to improve your speed and claims to be able to predict your marathon finishing time.

The inventor of the workout, Bart Yasso, came up with this training session and says he would use it to determine his fitness level going into a marathon.

Who Is Bart Yasso?

Bart Yasso was the Runner’s World Chief Running Officer and is a bit of a legend in running circles. He has been dubbed by many as “the mayor of running.”

Yasso’s running accomplishments are worthy of mention:

• He’s run marathons on all seven continents.
• He won the U.S. National Biathlon Long Course Championship in 1987 and the Smokey Mountain Marathon in 1998.
• He has also completed 5 Ironman races and the legendary Badwater Ultramarathon.

To further cement his legacy, Bart Yasso has been inducted into the Running USA Hall of Champions.

How Do You Properly Perform Yasso 800s?

The goal of Yasso 800s is to build up to 10 x 800 meter intervals on a track.

The amount of time, minutes and seconds you can hold for the workout are supposed to correlate to the hours and minutes it will take you to finish the marathon.

For example, a runner who can run 3 minutes and 20 seconds for all the 800m repetitions should theoretically have a marathon finish time of 3 hours and 20 minutes.

Many marathon plans will have you do several sessions of Yasso 800s spread out over a 12-16-week program.

Some earlier sessions will start with 4-6 reps of 800m. Throughout your training, you will add reps to the session until you can complete 10x800m at your marathon goal time pace.

Is It An Accurate Marathon Result Predictor?

Yasso 800s are a popular workout to predict your marathon finishing time, but are they really accurate?

A quick Google search will lead you to a host of articles and runners praising the workout and saying that it accurately predicts their finishing time.

Bart Yasso himself has said that when he can do the reps in 2:45, he has run a 2:45 marathon. Same for 2:50 and even as specific as 2:37.

On that same Google search, you will likely find a lot of coaches and athletes telling you that Yasso 800s are a poor predictor of marathon finishing times.

Running coach Jeff Galloway, among other coaches, believes there are better workouts you can run to prepare yourself for the marathon and predict your finishing time.¹⁰Jeff Galloway | The official site of Run-Walk-Run. (n.d.). Retrieved February 15, 2024, from https://www.jeffgalloway.com/

While Yasso 800s are a popular workout for predicting your marathon finishing time, the truth is there is no scientific data that shows that it does so accurately.

For some runners, there may be some correlation between the workout and their finishing time, but this is far from a guaranteed occurrence.

So you can consider your Yasso 800 timings to be a ‘rough guide’ of your marathon finishing time, rather than a clear indicator.

Is It A Good Workout For Marathon Training?

In reality, Yasso 800s are not a great marathon-specific workout.

When designing a workout for a specific race, two things should be considered: the length of the race and the pace that will be run. 

Most workouts should be focused on helping the runner prepare for one or both of these variables.

The marathon is 99% aerobic.

Workouts for the marathon should be designed around running close to your goal pace. These could include:

• Tempo Runs
• Intervals
• Fast finish long runs

The purpose of the workouts would be to have the body experience the demands of your marathon pace and develop adaptations to be able to hold it for the full marathon distance.

A Yasso 800 workout is going to have you running paces that will be anaerobic.

While there are benefits to doing an anaerobic workout during your marathon training, this workout will not be specific to the demands of the marathon.

The reps will be too short, and the rest will be too long.

For example, let’s say we have a runner hoping to run a 3-hour marathon to qualify for Boston.

If this runner were to do Yasso 800s, they would need to run two laps around the track in 3 minutes.

This would be a 6-minute mile pace. A 3-hour marathon is the equivalent of running a race pace of 6:52 per mile. That’s almost a 1-minute difference in pace.

For this runner, the 6-minute pace is closer to their 5k or 10k race pace. So our runner is doing 5 miles of intervals at 5k-10k pace while getting 3 minutes of rest between each rep.

This isn’t a workout that will produce meaningful results for a runner hoping to improve their marathon time through speedwork.

So what should you do instead?

The marathon is a difficult race.

Most runners will be running for 3.5-5 hours. This is a long time to be on your feet. Fueling becomes important to avoid hitting the wall, as does pacing correctly so you don’t bonk with several miles of race left.

A good marathon workout should have you practicing the marathon pace for extended periods of time. This can be achieved through several different workouts.

Here are a few examples:

The Best Marathon Training Workouts To Improve Performance

#1: Long Run With A Fast Finish

A great marathon workout can be implemented in most of the long runs you are already doing.

Set off on your long run as you normally would. However, for the last 30-60 mins, you will increase the pace to your marathon pace. An example of our 3 hour marathoner could look like this:

10 miles at easy/moderate pace (7:30-8:00 per mile)
4 miles at marathon pace (6:52 per mile)
2 mile cooldown
Total: 16 miles

This run will accomplish several goals that make it a better marathon workout than Yasso 800s:

• Running your actual marathon pace and getting a feel for it.
• Running your marathon pace on tired legs which will prepare you for the later miles in the race.
• Allow you to practice fueling on longer runs and while running at marathon pace.

This workout can easily be adjusted for more or less time at pace and longer or shorter distances.

#2: Cut Down Intervals

This is a great workout to get in a lot of time at marathon pace with some short jogging breaks to recover. These can be broken down into miles or minutes. Some examples could include:

5-4-3-2-1

• 5 miles at marathon pace, 5 minutes easy recovery jog
• 4 miles at marathon pace, 4 minutes easy recovery jog
• 3 miles at marathon pace, 3 minutes easy recovery jog
• 2 miles at marathon pace, 2 minutes easy recovery jog
• 1 mile at marathon pace, 1 minute easy recovery jog

25-20-15-10-5

• 25 minutes at marathon pace, 3 minutes easy recovery jog
• 20 minutes at marathon pace, 3 minutes easy recovery jog
• 15 minutes at marathon pace, 3 minutes easy recovery jog
• 10 minutes at marathon pace, 3 minutes easy recovery jog
• 5 minutes at marathon pace, 3 minutes easy recovery jog

Both of these workouts provide you with double-digit miles run at marathon pace while giving you short breaks to recover.

The workouts can easily be scaled down by removing the first, longer interval or by increasing the recovery between the reps.

For these workouts, be sure to do a proper warmup and cooldown.

These workouts will give you a much better idea of what your marathon finishing time will be.

While no workout will predict your finishing time with 100% accuracy, long workouts run at your goal marathon pace will be a much better indicator of your finishing time than Yasso 800s.

For more long run variation ideas, check out this next guide:

The Marathon Long Run: Essential Guide + Variations To Try

References

• 1
  Daniels J. Daniels’ Running Formula. 4th ed. Human Kinetics; 2021.
• 2
  Billat V. Interval training for performance: a scientific and empirical practice. Sports Med. 2001;31(1):13-31.
• 3
  Midgley AW, McNaughton LR, Wilkinson M. Is there an optimal training intensity for enhancing the maximal oxygen uptake of distance runners? Sports Med. 2006;36(2):117-32.
• 4
  Joyner MJ, Coyle EF. Endurance exercise performance: the physiology of champions. J Physiol. 2008;586(1):35-44.
• 5
  Tanda G. Prediction of marathon performance time on the basis of training indices. J Hum Sport Exerc. 2011;6(3):511-20.
• 6
  Daniels J. Daniels’ Running Formula. 4th ed. Human Kinetics; 2021.
• 7
  Riegel PS. Athletic records and human endurance. Am Sci. 1981;69(3):285-90.
• 8
  Tanda G. Prediction of marathon performance time on the basis of training indices. J Hum Sport Exerc. 2011;6(3):511-20.
• 9
  Foster C, Florhaug JA, Franklin J, et al. A new approach to monitoring exercise training. J Strength Cond Res. 2001;15(1):109-15.
• 10
  Jeff Galloway | The official site of Run-Walk-Run. (n.d.). Retrieved February 15, 2024, from https://www.jeffgalloway.com/