How to Measure Intensity Distribution

Is 80/20 really the best mix of intensities? And what's the best way to categorize training? Dr. Seiler has a simple method to get you started.

Pathways Logo graphic interpreting polarized training method as 80/20 mix of intensities, from green to yellow/red

Many athletes who are new to polarized training struggle with how to measure the time they spend in the different zones. Most training software packages allow you to graph the time spent in each heart rate or power zone over the course of a week, but even that doesn’t always indicate whether your training is truly polarized. 

For example, if you do a high-intensity workout with 10–20-second efforts, your heart rate may never go above your anaerobic threshold. So, even though this is clearly a zone 3 workout, a heart rate distribution curve will show that nearly all of the work was done in zone 2.  

This is why Dr. Seiler recommends that athletes focus on the session goal or purpose. If you did high-intensity intervals in a session, then the entire session can be counted as a zone 3 workout. To achieve an 80/20 distribution of intensity, plan on one of every five workouts being hard and the rest easy.  

If you are using a power meter for cycling, running, or rowing and you want to see the distribution of your power, keep in mind that with a polarized approach to training your time in zone 1 could be as high as 90 percent. Case in point, if that high-intensity session with 10–20-second efforts is an hour in length, only about 12 minutes will be accounted for as zone 3 power. The rest will be zone 1. 

Video Transcript

80/20 and Time in Zone vs. Session Goals

The 80/20 term has really been associated with polarized training. Correct me if I’m wrong, 80/20 was something that was a session observation, that wasn’t necessarily a percent split. What exactly is 80/20? What should people be understanding from that?

The early papers that we published, in particularly the very first one where we talked about this, we used what we called session goals.

There are different ways of quantifying intensity:

Time in Zone: Use heart rate from your watch [or power], and set up the zones. It will automatically tell you time in zone. You can square that off a bit, and use a modified time-in-zone.

Session Goals: If it was the interval session, and you did 6 x 4 minutes, and it was really tough, even though you did a warm-up and a cooldown on each end that was easy, that whole session is now going to be called a hard session, and we’re going to put it in the high-intensity bucket. In other words, it’s a categorical intensity distribution.

At that time, we used low intensity, threshold intensity, and high intensity as the three categories based on the key intent of the session.

  • Were they doing three times 20 minutes at threshold?
  • Were they doing 6 x 4-minute VO2max intervals?
  • Were they doing a 2-hour easy long run?

Then, we look at heart rate and lactate to verify that. That was how we were placing these workouts in these different categories–over 400 workouts in that first study–and then getting a distribution that was around 80 percent low intensity, and about 20 percent the rest. Meaning some threshold, and in that study even more of the more high intensity like zone 4 or 5 in a 5-zone model. This was cross-country skiers. That was the impetus because we’d already seen a bit of the same and Kenyan runners from other studies from French scientists. We were piecing together this data, and then we said, we are calling this a polarized model of intensity distribution. But it was based on session distribution.

I had a PhD student that came back, and we looked at this and said well, if they’re 80/20 based on session distribution, what are they based on time-in-zone typically? What’s the calibration? Then what you’ll see is it might be 90/10 in these in these high-performance athletes that are doing 20-plus hours a week. In rowing, we even saw we published one study that was more like 95 percent based on time-in-zone. You can get different numbers depending on whether you’re using heart rate, whether you’re using power, or you’re using intent, the session goal. But it’s usually somewhere in that 75/25, 80/20, and [upward], meaning even a higher amount in the low-intensity range, depending on how you quantify it.

A Simple Plan to Account for Intensity

What do you think tends to work out best for athletes? How should the athlete be looking at this themselves when they’re quantifying it?

I would just start simple with roughly three out of every four workouts in that low-intensity range. One of them may be longer than normal, but [all three are] going to be in that low-intensity range. [And] as a starting point, if you just think of four workouts, one out of four [25 percent] is going to be kind of something like an interval session or threshold session, it’ll be tough. Mentally you’re geared up, you’re ready, you got it, you’re thinking more aggressively about maintaining a certain power.

Then three out of four, it’s more [low-intensity with some] duration focus. It’s more like putting in the work and enjoying it, you’re being purposeful, technically, and so forth. But, it may be a 2-hour ride or a 3-hour ride or a 90-minute run, and so those are the bread and butter. In what we see is with elite athletes, if you look at their distribution, they do a whole lot of those workouts. It’s not necessarily super exciting, it’s just doing the work to be honest. I’m not trying to say this is the most exciting way to train, in fact that some people will struggle with it at first because they they want to somehow make every workout a bit tougher and get that adrenaline rush. What they end up doing then is then they land in that staccato mode is where or every workout is pretty hard. Then their ability to mobilize actually gets worse; they kind of get flat.

We can literally see that in it with heart rate: [Athletes will] say I can’t get my heart rate up or they may not even know they can get the heart rate up because it’s been so long; they do it so much that now they their max heart rate–that they think is their max heart rate–is depressed. It’s been depressed for months. I had a I had an athlete tell me one time, “You know what? I started polarizing my training and my maximum heart rate went up 10 beats!” I said, “Yeah, because you’ve been overreached for . . . I don’t know . . . years!” He was astounded.

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