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Special Workout :: Yasso 800 - The Marathon Pace Workout with a Twist

The Yasso 800 is a marathon training session built on 800 metre repeats (twice around a standard 400 metre track), run at a constant pace with a jog of equal time between each. The minutes and seconds per repeat are meant to predict your marathon finish in hours and minutes, so 10 to 12 repeats at 3:30 would suggest a 3:30 marathon. It is a genuinely good workout but only a so-so predictor. Below: how to run them, pace and recovery, how many repeats to build up to, how well they predict marathon and half marathon pace, and whether the session is worth your time.

Named after Runner's World editor Bart Yasso, this session has a solid following, and plenty of marathon runners stake their goal time on it. A prediction that looks almost too good to be true usually comes with small print, so it pays to know where it can mislead you before you build a race plan around it.

I'll cover the following topics:

1. So, how do you do this marathon pace workout?
2. How do you run Yasso 800s properly, with a pace chart?
3. How many repeats should you do, and how do you build up?
4. Are Yasso 800s helpful in predicting your marathon pace?
5. Is there value in the Yasso 800 as a marathon pace indicator?
6. Using the Yasso 800 as a half marathon pace guide.
7. Are Yasso 800s a good workout?

So, How Do You Do This Marathon Pace Workout?

The Yasso 800 revolves around 800 metre repeats, which you run at a constant pace.

The time you spend running those 800 metres in minutes is a prediction of how fast you can run your marathon in hours.

Here's the twist — you're not running at marathon pace. But if you can complete 10–12 of these 800 metre repeats at a given time, the theory says your marathon finish time matches it.

Take a practical example. Say you run your Yasso 800s at 3:30 min per 800 metres, with a 3:30 min recovery jog in between. Complete that 10–12 times in a row, and the prediction is a 3:30hr marathon.

Doing your repeats at 2:50 min per 800 metres, with a 2:50 min jog in between? Your predicted marathon time is 2 hours and 50 minutes.

Almost too good to be true... And yes, it often is. I'll explain why shortly.

It is still a good workout, so don't take what follows as a criticism of the session or its creator. In fact, I'd argue it has a really good use for the half marathon — more on that below. Let's move on.

Running Your Yasso 800s: Track, Pace and Recovery

Run them on a 400 metre track if you can. Two laps make one repeat, so pacing is easy. A 3:30 repeat is 1:45 per lap, and you can check your split every 400 metres. No track? Use a flat, quiet stretch of road measured with your watch — hills and headwinds wreck the numbers.

Here is how the session goes:

• Warm up with 10–15 minutes of easy running, then 3–4 short strides.
• Run 800 metres at your target time. Not faster, not slower.
• Jog for the same amount of time as the repeat (roughly 400 metres). Keep moving — don't stand or sit.
• Repeat until you reach the number of repeats in your plan.
• Cool down with 10 minutes of easy running.

The trick is even pacing. Run repeat one too fast and you will pay for it by repeat seven. That's the most common mistake I see. If your last repeat is the same as your first, you picked the right pace.

Here is the chart to keep handy. The marathon column is the Yasso prediction. The half marathon column uses the same conversion I cover further down this page.

One thing: the number only counts if you complete all 10–12 repeats at that pace. Six repeats at 3:30 tells you very little.

How Many Repeats, and How Do You Build Up?

The commonly cited build-up is simple. Start with 4 repeats in one session, add one a week, and reach 10 about two weeks before your marathon. One session a week, no more.

My advice to you: keep it sensible. Don't schedule Yassos the day after your long run, and don't add a repeat in a week where you feel flat. Repeat the same number instead — a consolidation week does you good, and the workout will still be there next week.

If a weekly Yasso feels like too much, there is a lighter option. Do a 6-repeat session mid-build, then the full 10–12 once, three to four weeks before race day. That's it. I come back to this at the end, because for most marathoners I'd say once or twice per cycle is plenty.

Are Yasso 800s Helpful in Predicting Your Marathon Pace?

Here's the honest answer: not reliably.

Think about what you're comparing. 800 metres against 26.2 miles. A marathon is about 53 times the distance of a single repeat. That's a massive difference — and no clever formula bridges it completely.

Running 800 metre repeats at a faster clip simply isn't a great comparison for an event that demands a sufficiently developed aerobic base. Your marathon requires mileage. It requires long runs. It requires time on your feet that 800s cannot replicate.

In my experience, the Yasso 800 tends to be somewhat too positive about your marathon goal time. There is a lot more involved in running a three hour marathon than completing 10–12 x 800 metre repeats in three minutes. It's nice. It's gimmicky. But unfortunately it's not that simple.

Half marathons are a better predictor for marathon performance — provided you've done the work your marathon demands. Use my marathon calculator page to find out more and Bob is your uncle!

Is There Value in the Yasso 800 as a Pace Indicator?

In several forum discussions I've seen runners claiming that Yasso 800s do predict your marathon time — but only if your heart rate stays at the same level across all 800 metre repeats.

If it creeps up during the workout, you probably won't be able to run your race at the predicted time.

I haven't tried this myself, but I tend to believe it. When your heart rate holds steady through a workout at roughly tempo effort or above, you're demonstrating you have little difficulty at that pace. That's meaningful.

Before you trust any Yasso number, be honest about your long runs. Have you done several of 16–20 miles, ideally with marathon pace blocks inside them? If not, treat your Yasso time as a ceiling, not a forecast.

My recommendation is to use more than just the Yasso 800 when you're working out your predicted race pace. I prefer:

• Recent half marathon race times
• Combined with knowledge of your current long run, tempo run and interval paces.
• Importantly, do some marathon goal pace sessions and see how they go. Long runs with marathon pace blocks are really big predictors and great training!

Take all of that information, then cross-reference it with your Yasso 800 data. Together, those sources give you a much clearer picture of how fast you can run your next marathon. Relying on the Yasso 800 alone is not sufficient.

Also see my tips for running a marathon page to learn everything necessary about marathon pace training and marathon pace strategy.

Using the Yasso 800 as a Half Marathon Pace Guide

Here's where I think you'll find the most practical value: use this workout as a half marathon pace indicator. The marathon is an unpredictable beast — many of us know all too well how those last six miles can unravel. The half marathon is far more predictable. With sensible training and pacing, you can be confident of finishing strongly.

So, how do you use the Yasso 800 as a half marathon pace indicator? Fair warning — there are a few steps involved and some maths. But I'll lay it out clearly, and I'll walk you through two examples as well. I've used this approach myself and with clients, and I've found it genuinely helpful. Worth persevering through:

1. In the build-up to your half marathon you've been doing some Yasso 800s and found you can run 12 x 800m at 3:30 min.
2. Theoretically, this corresponds to a 3hr30 marathon. Now, find the equivalent half marathon time using this race conversion calculator. Fill in 3hr30 for a marathon and predict the half marathon time.
3. If you've done it correctly, it predicts a half marathon of just below 1:41. So, Yasso 800s at 3:30 min point to a half marathon of a little less than ~1:41.

Let's do another example.

Example 1
Suppose you have recently run a 10k in 43 minutes. Using the race conversion calculator in the link above, you'll work out that your predicted half marathon time is about 1:35 and your predicted marathon time is about 3:18.

When you can complete a Yasso 800 workout of 10–12 x 800 metres in 3 min 18 per repeat, with 3 min 18 sec jogging in between, you have another strong indication that you can indeed hit that 1:35 half marathon time.

Makes sense?

Let's walk through one more example.

Example 2
Suppose you have recently done a 5k race in 25 minutes. Using the race conversion calculator, you'll find a predicted half marathon time of 1 hr 55 mins and a predicted full marathon time of just under 4 hrs.

So, if you can complete a Yasso 800 workout of 10–12 x 800 metre repeats at 4 mins per repeat — with a 4 min jog in between — that gives you solid guidance that 1:55 is indeed feasible.

Of course, there are other half marathon goal pace sessions you can do — the link will give you some good examples.

When deciding on your race pace — whether that's a half marathon, full marathon or any other distance — your best approach is to use a number of different references. Use a recent race. Use some recent training paces. And use the Yasso 800 alongside those. The big mistake is relying on intuition or just one indicator. That single indicator may be overly positive, and that can set you up for a painful day out.

I know some runners who are incredibly good at short distances like the 800m — they'd hold 3 min repeats all afternoon — but they'd really struggle hitting a 3hr marathon without sufficient long runs behind them.

Are Yasso 800s a Good Workout?

Yes — Yassos are a good workout. There is nothing wrong with 800 metre repeats, and doing 10–12 in a row at a moderately hard pace is a very decent session indeed. You cover a solid amount of mileage at quality pace.

That said, in terms of marathon preparation, it sits alongside a whole arsenal of good workouts — and some of those are distinctly better. Long runs, marathon pace sessions and tempo runs should take priority in your training schedule.

My recommendation: do Yasso 800s once or twice in a marathon cycle. Vary your distances and speeds to build real variety into your training, and you'll arrive at the start line better prepared. Don't sacrifice a large chunk of your programme to Yassos — they don't warrant it for a marathon build.

Use them as a useful workout first, and as something of a predictor second. They're interesting, they've earned their popularity, and as a half marathon pace indicator they can certainly be helpful. Just don't hand them the wheel and expect them to drive your entire race plan.

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