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by Dave Milner

Distance running, on the surface, seems like a simple sport. One puts one foot in front of the other in quick succession for a specific, often pre-determined, distance, and one usually does this, when a piece of waxed, waterproof paper with a number on it is pinned to our chest, as fast as we possibly can. With some training under our belt, we can usually predict how long it will take to cover those pre-determined distances. Run a 5K, and you can probably get a fairly good handle on how long it might take you to cover 10K. Run a 10K and you can probably figure out how long it will take to cover 10 miles.

Marathon running - extending those steps to a distance of 26 miles and 385 yards - brings to the table a myriad of confounding variables, such as caloric intake, changing weather, and, more importantly, the training regimen that preceded the race, and predicting one’s finish time becomes somewhat trickier. So when the writers at Runner’s World magazine tell you that they have discovered a simple track workout that can accurately predict your marathon finish time, you sit up and listen, right?

Show me a marathoner who hasn't heard of Yasso 800s and I'll show you one that has had his head in the sand lately. Bart Yasso, a writer at RW, had been using a track workout consisting of ten 800-meter repeats with the recovery jog period equal in length to the time of the hard effort. He discovered, surreptitiously, that if he could run his 2-lap reps in 2 minutes and 50 seconds, working up to 10 reps, he’d be in 2 hours 50 minutes marathon shape, and if he ran 10 of them in 2 minutes and 40 seconds, he’d be in 2 hours and 40 minutes marathon shape. When he told RW senior editor Amby Burfoot about the workout, he was shooting for 2:37. Burfoot, intrigued, crunched the numbers and talked to over 100 runners of widely differing abilities (from a 2:09 marathoner to several well over 4 hours), and as Burfoot reported “darn if the Yasso 800s [as he coined them soon after] didn’t hold up all the way down the line.”

Bart begins his Yasso 800s a couple of months before his goal marathon. The first week he does four. On each subsequent week, he adds one until he reaches 10. The last workout of Yasso 800s, he advises, should be completed two weeks before the marathon.

Wow, the concept sounds great, doesn't it? Want to run a 3 hour marathon? Train to run 10 x 800 in 3 minutes. Want to run a 4:00 marathon? Train to do the 800s in 4:00. Want to qualify for the Olympic Trials? Do the Yasso 800s in 2:22? What could be more simple than that? Read Runner’s World and you'll be convinced that Yassos are the key to getting your marathon time goal. Of course, do your long runs, but definitely don't skip the Yassos because, Burfoot writes, “this is the workout that will get you to the finish on time.”

And in some senses, Yassos seem to have some merit. Take a look at some online training pace calculators, even the the one on, or have a gander at Daniels’ Running Formula, and you'll note that a 3:00 marathoner's suggested VO2max interval pace would be about 2:58/800. A 4:00 marathoner's suggested VO2max interval pace would be about 3:56/800. That seems quite close, doesn't it? Well, theoretically, yes.

But, unfortunately, as much as Runner’s World attempts to simplify an activity that has so many variables that can impact it, running - especially marathon running - just isn't that simple.

There are a number of factors that need to be kept in mind when considering whether to put your stock into Yasso 800s. First, remember which energy systems the workout is stressing most and which energy systems the marathon stresses most. Second, note the differences in those paces. Third, ask yourself this: Is there a better workout you could be doing?

While we’re asking ourselves questions, try these ones:
What energy systems do Yasso 800s stress most? Answer: the VO2max system. What about the marathon? Well, that’s a primarily aerobic event, run at a pace lower than your lactate threshold. So, in effect, with Yasso 800s, one is attempting to determine performance potential at a stamina-oriented event by doing a much more speed-oriented workout. Still with me? If so, you’ll realize that this is not the smartest approach.

The simple fact is that most marathoners these days have not developed their aerobic systems nearly as well as they have developed their speed. You can approach maximization of your speed very quickly, but it takes many years to fully develop your aerobic system. For a good visual of the differences here, just consider the paces. Running 800s in 3:00 means you're running about 6:00/mile. A 3:00 marathon is a little under 7:00/mile, over 50 seconds per mile slower than the workout. As your times increase, so does the spread. A 4-hour marathoner would be running Yasso 800s over 1:00/mile faster than goal marathon pace. That's a pretty big difference in paces when trying to predict what you are capable of in one by doing the other.

That difference is very significant because most runners are far better trained for the shorter events, like 5K, than they are for the longer ones. Don't believe me? How many 18:45 5k runners do you know who can run a 3:00 marathon? At the time of writing this there were 37 over-40 men in the state of Tennessee who had run 18:45 or better for 5K. Number of over-40 guys with a sub-3 hour marathon under their belt? Six. How many 5K runners with a PR of 25 minutes do you know who can run a 4:00 marathon? Probably not many. But those are equivalent performances, if one is equally well trained for both events.

But the truth is that most people are more well trained for the shorter events, and hence Yasso 800s, than they are for the longer events like the marathon. Need more proof? When training for my second marathon, for which I was aiming to crack 2:40, I did several Yasso 800 workouts, but because I was also capable of racing 2:00 for 800 meters at that time, running 2:40 halves was extremely easy for me. Not because I was a well-trained marathoner, necessarily, but because I had good leg speed and efficiency.

But Yassos still make a good workout, right? Of course. Are they the best workout that a marathoner can do? No, definitely not. A marathoner would be better served by doing longer repeats at around the pace of the Yassos, but of distances more like 1200-1600 meters, or longer lactate threshold pace repeats of 1 to 2 miles with short recoveries in between. Doing 800s at times in a training plan is not a bad idea, though. Sometimes, when our motivation is in a dip, 800s are about as much as our attention span can handle without having to reset itself. However, placing too much focus on Yasso 800s is taking time and energy away from workouts that can be far more effective in preparing for the demands of a long event like the marathon.

Moreover, there is a considerable body of evidence that suggest that Yasso 800s aren’t quite as accurate as RW would have you believe. Online über-coach, Greg McMillan, has reported that many people wind up running 5-7 minutes slower than their Yasso times. I know many runners who tried using Yassos to predict their marathon performance, and the typical result was that they fell 10-15 minutes short of what the Yassos predicted, sometimes even more.

So there is a good chance that if you go out at the pace that at which your Yassos predict you could finish the marathon, you will probably be going through the ‘half’ 5 to 10 minutes faster than you should be. That’s not good, since most 26.2-mile experts agree that, for every minute you are too fast at the half-way point in a marathon, you end up losing at least two to five minutes in the second half. Therefore, you could be costing yourself 10 to 50 minutes in the second half and 5 to 40 minutes overall. That adds up to two things: a time much worse than you were capable of and a whole world of hurtin’ on the back thirteen.

Want to avoid that painful second half and a personal worst that everyone will see when the results are posted online? This pearl of wisdom is simple. Don’t use the Yasso 800s (as prescribed by Runner’s World) as your 26.2-mile crystal ball. A better predictor, if you’re looking for one, would be to take your time at a half-marathon about 6-8 weeks before the big day, double it, and 6-10 minutes (depending on what kind of weekly mileage you’re logging in preparation).

Do Yasso 800s make a good workout for someone training for a marathon? In moderation, yes. Are they a fun, entertaining way to incorporate a little excitement and confidence boost into a speed workout? Sure. Do Yasso 800s make a good predictor of marathon performance? No, at least, not to the degree Runner’s World would have you believe. What I have found, in training groups of marathoners ranging in ability from 2:50 to 4:45, and using myself as a guinea pig, is that the better the runner, the less recovery should be allowed between the intervals in order for the Yasso 800s to have any predictive value.


* Try the 10 x 800m with less recovery between (sub-2:45 marathoners: take 30 secs recovery; 2:45-3:00 marathoners: take 60 secs recovery; 3:00-3:15 marathoners: take 90 secs; 3:15-3:30 marathoners: take 2 minutes secs; 3:30-3:45 marathoners: take 2:30 recovery; 3:45-4:00: take 3:00 recovery).
* Try a ladder workout of 1000-1000-1200-1600-1200-1000-1000 (total of 8000m, same as original Yasso 800s workout) with equal time recoveries.
* Do 8 x 1000m or 5 x 1600m repeats at the Yasso pace, with equal time recoveries.


The main problem with Yasso 800s is that either the recoveries are too long or the repeats too short. With a little fine-tuning – that would make them less gripping copy on RW’s glossy pages – they can make for a great workout, and have greater predictive value.

Yasso 800s, whether Yasso realized it or not, are a VO2 max development workout. That is, they are intended to improve your ability to consume oxygen. Most experts concur that a runner has to be working at a high heart rate for between 3½ to 5 minutes. Then you recover for the same amount of time you just ran, and then you do it again. You can make the repeats shorter, if you also reduce the recoveries.

If you’re doing your 800s in 4:00 or over, then the Yasso 800s are probably okay for you. You’ll be working on your oxygen uptake ability for about the right period of time. But if you’re doing your 800s closer to, or under, 3:00, you should either reduce the recovery period or extend your Yasso 800s to 1000, 1200, or even 1600 meters, at the same pace (as long as the total length of the repeats does not go much over 5 minutes)

DAVE MILNER is the editor and publisher of Tennessee Running, and has run five marathons with a best time of 2:45:23. In his best adapted Yasso workout, he averaged 2:36 for ten 800-meter repeats with 30 seconds recovery.



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