Can Yasso 800s Predict Marathon Time?

Audio Transcript

Michael Hammond: Hey, Runners Connect fans. Welcome to another episode of the Run to the Top Extra Kick podcast. Michael here to answer a question from Rob about Yasso 800s.

Rob: Hi, I really appreciate the daily podcast. My question is about Yasso 800s which sometimes show up in marathon training plans.

Supposedly they have a predictive power in terms of estimating the marathon finishing time. I’m wondering if that’s true, and if the workouts have a benefit beyond predicting marathon times. Thank you.

Michael: That’s a great question, Rob. Most are probably familiar with Yasso 800s.

For those who are not, what Yasso 800s are, is a race predictor workout, at least that’s what they are claimed to be. It’s 10 by 800 meters, and you take equal rest.

Let’s say you’re doing all those 800s in four minutes. That’s eight-minute mile pace, then you take four minutes’ rest between each one. That’ll be 10 times 800 with equal rest in between. Four minutes 800, four minutes’ rest, repeated 10 times.

What this is known to do, at least what most people think of as these Yasso 800s is they’re going to be this accurate predictor.

Whatever pace you can average for those 10 by 800s, you’re ending up ultimately running the workout all out.

Whatever you can average for that, this is their claim, that’s going to be an accurate representation of what you can do for a marathon.

The big caveat to us is that there’s no science to support it. That’ always going to be a red flag for us at Runners Connect because we try to make everything very science-based.

We go by experience, of course we do, but at the same time if something has no science at all, no research done whatsoever to prove, then we’re not going to read too deep into it, at some point it becomes the correlation vs causality issue.

Just because something happens at the same time or two things happen concurrently, does not necessarily mean there is a causality there.

For a funny story that Jeff put on our article on this subject, he talked about how the number of U.S. highway fatalities perfectly correlates to the number of fresh lemons imported from Mexico. There’s a legitimate study that was done on this topic.

Obviously, that’s ludicrous to think that there is actual causality there, it’s just correlation, it’s just coincidence when it comes down to it. That would be unbelievable if that were a correlation.

The reason that he put that story is to show that just because you can run 10 by 800 at a certain pace, and maybe you run a marathon at that same pace, does not necessarily mean that there’s any causality there, that it was the Yasso 800s that predicted that time.

It could just be coincidental that you did this workout at the same pace. Note there that there is no established causality between the two.

The other one is, it’s not marathon-specific. We’ll get into this a little later, but it’s not a marathon-specific workout.

For one thing, the way we look at it, we think that usually the time that’s predicted is going to be somewhere maybe five, six, minutes too fast, and this is because 800s don’t give you the proper guidance, they just don’t.

Think about it like this. Think about six-minute-per-mile pace. Anybody, even a four-hour marathoner can go run a 400 meter in 90 seconds. That’s not very hard.

But if you think about a six-minute mile so you multiply that by four. Four times 400 meters in 90 seconds with no rest, that’s a mile in six minutes, that’s not easy, that’s hard.

800s are longer than 400s but they’re closer to 400s than they are to a mile, so it’s not a proper indicator.

The other reason is fuel. This type of workout does not have the same fuel utilization as the marathon.

When we get into the marathon, we get into both carbohydrate and fat utilization.

There’s utilization of energy when you’re late into a run, when you’re long into a run, been on your feet for a long time.

10 by 800 is a decently long workout, but it doesn’t take you that long relative to what a marathon is going to take, so totally different energy systems when it comes down to it.

For a workout like a 10 by 800, because it is so much shorter, and because the intervals are so much shorter, you can get away with less.

You don’t have to focus on fuel. Your body doesn’t have to dig into its fat stores or anything like that. You can get away with less fuel and less focus on fuel.

Yasso 800s are a VO2 max workout when you come down to it. From what we found in our own research and other studies, VO2 max workouts don’t increase fuel efficiency at all, that’s what we were talking about right before this.

In addition, they don’t target the aerobic threshold, so at that point you’re left wondering well, what is this for?

An important distinction, VO2 work has its place in marathon training. What we are arguing is that Yasso 800s have a limited benefit to marathon training.

Not that they have no benefit; it’s just that they have a limited benefit. Of course, VO2 work has its place in marathon, and we prescribe it ourselves, it’s useful.

But too much emphasis has been put on this single workout especially since a lot of times they’ll be saying to do this at a very crucial point prior to your marathon.

When you get down to the last 12 weeks before your marathon, you’re in the crunch time, you’ve got to fit in some quality workouts and every day counts when you get to that point.

If you’re taking a whole workout day and putting in something like this, a VO2 workout, it doesn’t have a place at that point in training and it doesn’t make a lot of sense. That’s when you should be doing the real marathon-specific work.

For instance, two big ones that we do. One is the two by six-mile workout, where you run two times six miles with a decent amount of rest in between.

That’s a great marathon workout because you can’t fake that, you can’t get away with, Oh because you’re maybe a little faster, maybe a little bit more foot speed than you do in endurance.

You can get away with doing some 800s but you can’t get away with doing two by six miles. That’s a solid predictor work out there.

Then we have the steady long-run combos, another solid one where you do your long run on Saturday or Sunday, and the day before, you do a steady run, maybe four to eight miles at roughly marathon pace.

Those are some good marathon-specific type sessions that make a lot more sense at that point in training.

A better predictor would be the fast finish long run. A fast finish long run is a tremendous predictor.

You do anywhere from 16-20 miles, maybe a little bit more for advanced people, but typically, people are going to be in that 16-20 range, and you do the last 6-10 miles at your goal marathon pace or faster.

If you’re doing eight miles at your goal marathon pace, maybe do five or six miles at your marathon pace and then you try to finish off a little bit faster.

What this is going to do is it’s going to teach your body to run at a marathon pace when you’re tired.

I know it sounds obvious, but if you go on a 20-mile long run and you don’t start the 10-mile fast finish until you’re 10 miles into the run, then you’re already fatigued, even if you are running easy, that’s still quite a bit of time on your feet.

So, now we’re talking about that fuel utilization, the fat and carbohydrate, working on your own fueling as well, which is incredibly important, and will play a huge difference on race day if you’re doing it in training.

The fast finish long run is far superior in terms of a predictor workout.

We are not saying Yasso 800s are bad, it’s just that if you want to do a nice predictor workout for your marathon, go with the fast finish long run.

All in all, it’s not that they’re worthless, but don’t put too much stock into the Yasso 800s.

Runners Connect fans, that’s it for today.

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