One of the big debates in endurance sports these days is about “training intensity distribution,” which is a fancy term for how much of your training time you spend going easy, medium, or hard. The dominant paradigm is the polarized distribution, which calls for a lot of easy running, a little bit of hard running, and not much in the middle. But there are various other viewpoints, including the currently fashionable Norwegian training, which puts a heavy emphasis on medium efforts.
One way of exploring which training distribution is best is to look at the training diaries of the best endurance athletes in the world. That’s how the concept of polarized training was born, and it’s why Norwegian training is rising in popularity. Of course, this isn’t as reliable as a randomized trial. Maybe most elite athletes train in a certain way because it’s popular, not because it’s objectively better than the alternatives. And even if we figure out the best way for elites to train, it’s not clear that those insights will apply to the rest of us.
Another option to assess training intensity is to look at how the unwashed masses train: to sift through reams of data looking for the patterns and variables that predict the best race performances. That’s the approach taken in a new study in Sports Medicine, from a group of researchers led by Daniel Muniz-Pumares of the University of Hertfordshire and Barry Smyth of University College Dublin. They analyzed 16 weeks of training data leading up to a marathon for 120,000 runners who recorded their training in Strava.
To Run Faster, Run More
Before delving into the nitty-gritty of training intensity distributions, we should start with the elephant in the training room. By far the best predictor of marathon time was how many miles a runner racked up. The researchers divided their sample into half-hour finishing groups: the fastest group was the sub-2:30 marathoners, the slowest group was those between 6:00 and 6:30.
On average, the runners accumulated 28 miles per week over the 16 weeks prior to their goal race. But there were big differences. Sub-2:30 runners ran 67 miles per week, about three times as much as those running slower than 4:30 and 60 percent more than even the sub-3:00 runners. Here’s the weekly mileage (in kilometers, on the vertical axis) as a function of marathon finishing time (in minutes, on the horizontal axis):
This is the men’s data; the women’s data show essentially the same pattern. The four different lines show the average mileage during four different four-week blocks before the race. There are some slight differences—mileage is highest five to eight weeks before the race, for example—but the overall pattern is the same throughout: faster runners run more.
What the Training Intensity Distribution Reveals
You could be forgiven for thinking that this is painfully obvious. But what’s interesting is how the faster runners ran more. They didn’t just scale up their training proportionally compared to the slower runners. Instead, the difference was almost exclusively in how much easy running they did.
You can divide the accumulated training into three zones loosely corresponding to easy, threshold, and interval or race pace. (I won’t belabor the details of how they crunched the training data or defined the zone boundaries, but it’s based on calculating each runner’s critical speed using the approach I described in this article.)
When you break out the different training zones, you find that runners of all levels, from sub-2:30 all the way through 6:30 marathoners, did virtually identical amounts of hard zone 3 training. They also did very similar amounts of zone 2 threshold training. There’s a slight trend toward the faster runners doing a bit more, but it’s barely noticeable. All the variation—remember, there’s a threefold difference in total training volume—is packed into easy zone 1 running.
The graph below is a little busy (it once again breaks out the results into four-week blocks, even though the trends in each block are similar). The key point is that the red lines (zone 3) are flat, meaning that all the different pace groups accumulated similar amounts of hard running time. The orange lines (zone 2) are nearly flat. But the green lines curve sharply upward on the left side of the graph, showing that the faster runners do more easy running.
So It’s Polarized Training for the Win?
That depends on what you mean by “polarized.” There’s a fairly convoluted debate (which I summed up here) on the meaning of the term, but there are two key elements. One is the idea that most of your running should be easy. That’s often summed up (as in the title of Matt Fitzgerald’s 2014 book on the topic) as 80-20 running: around 80 percent of your running should be easy, with the other 20 percent medium or hard. Muniz-Pumares’s new results support this view.
The second element is the idea that you should avoid medium intensities, since they’re too slow to give you the benefits of interval training but too hard to recover from if you’re trying to run big miles. That is where the name “polarized” originally comes from, since most of your training is supposed to cluster at the extremes of easy or hard. But the new data doesn’t back this claim up: very few of the runners, whether fast or slow, were doing truly polarized training.
What the runners were doing instead is called pyramidal training. Classic polarized training might involve an 80:5:15 breakdown of easy, medium, and hard. Pyramidal training, instead, might be 80:15:5. Instead of avoiding the middle zone, you do a moderate amount. In practice, though, the distinction between polarized and pyramidal is hazier than it seems. Previous research has found that the exact same training plan might look either polarized or pyramidal depending on whether you calculate the intensity distribution using running speed, heart rate, or even the intended effort.
The bottom line, from my perspective, is that it’s not worth getting too wound up about the specific nomenclature. This data supports the idea of doing lots of easy running and modest amounts of medium or hard running. It doesn’t support the idea of avoiding the medium zone. Whether you call that polarized or pyramidal is up to you.
What’s Lost in Translation
As I noted at the top, this isn’t a randomized trial. We know that faster runners did more easy running than slower runners. We don’t know if doing more easy running would have turned the slower runners into faster runners. But even if it did, that assumes that the slower runners have the time or desire to run more—and that’s by no means a safe bet.
The fundamental assumption for elites is that their training is primarily limited by what their bodies can handle. Polarized (or pyramidal) training is supposed to be effective because it’s an optimal way of racking up the greatest possible combination of training volume and intensity. To max out what your body can handle in a given week, aim for that 80-20 split.
Meanwhile, out in the real world, the key question isn’t how much my body can handle. It’s how much training I can squeeze in before work or between picking up the kids and making dinner or whatever. The 3:30 marathoners are putting in about four hours of training per week. It’s not hard to believe that adding an extra hour or two of easy running on top of what they’re already doing would make them faster.
The trickier—but also more relevant—question is how to make them faster on four hours of training per week. Switching to an 80-20 split would actually mean doing less total mileage, because they would be replacing a big chunk of their medium or hard running with easy running. Sure, they would recover more quickly from each training session. But would they really end up going faster?
This is an open question, and I don’t think there’s any firm answer at this point. But my takeaway from all this is that we should think carefully about what constraints we’re imposing or accepting on our training. If time is really the issue, then spending more of that precious time running hard might make sense for you. But if “I don’t have time” is just another way of saying “I don’t want to,” or if you’ve been held back by the fatigue and injuries that often accompany hard training, then it’s worth considering doing more easy running. It’s the easiest and least risky type of training—and in this analysis, at least, it’s the one weird trick that distinguishes faster marathoners from slower ones.
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