The 80/20 Rule Doesn’t Work in Endurance Training

The 80/20 distribution rule in endurance training doesn't really work. An elite athlete will only spend two to five percent at a maximum, two to five percent in high intensity training, And in a hobby athlete, again, it will more be 40% to 60%. So let's think this through. But this 40% to 60% will be approximately the same one and a half to two hours.

So two and a half hours compared to one and a half hour of accumulated time at high intensity led to a net loss in mitochondria capacity. So bottom line is, what you want to do for your own training, or for the athletes that you coach, And it should be really obvious why the 80/20 rule, in terms of 80% low-intensity training, 20% high-intensity training, cannot actually work.

It is a ballpark number which you can use if you are, by chance, so to speak, in the correct range for weekly training duration. Let me explain why the 80%, 20% rule for intensity distribution in endurance training doesn't really work. Why? You will actually see it doesn't make any sense at all. And it's pretty logical, okay?

So hear me out. Let's assume you have an athlete with a relatively low training volume. Take myself, a few hours per week if I'm lucky, two, three, four hours of training maybe. Okay, so what does it mean? If you had, for example, exercise three times per week, 45 minutes each time, let's say, that means automatically that very likely, at least for most people, you will always have at least one rest day in between the training sessions, number one.

Number two, each training session is relatively short in time, half an hour maybe if it's running, 45 minutes up to an hour maybe if it's cycling. So that means there's always enough time for somewhat likely a sufficient recovery. Sufficient because the time between the training workouts is relatively long, plus the workout itself is relatively short.

A good marker to look at, one of the best markers to look at, is actually glycogen stores. Glycogen stores, so glycogen is the form of sugar, how it's stored in the muscle and the liver. For this case here, we're only interested in the storage and the muscle. So glycogen storage, if you exercise at the highest intensity that is sustainable, for example, maximal lactate steady states or threshold, simply put, the glycogen stores last about 60 to 90 minutes-ish, somewhere in the ballpark.

And then you need a minimum of two days up to three days to replenish. So let's think this through. For example, if I would have an hour of training available, and let's say 45 minutes to an hour whatsoever, and I do 10 to 20 minutes, 10 to 15 minutes warm-up, and then I do some high-intensity intervals, threshold or very high intensity, doesn't really matter for the sake of the example.

That means that my actually net training time at high intensity, even if it's only warm-up, interval, cool-down, is approximately, what, half an hour-ish at maximum 20 minutes. And the amount of glycogen I will burn is relatively small compared to how much time do I have to replenish it, meaning I will never really have the problem that I run out of it.

I can always replenish and always recover. And for several reasons, which we actually do cover in our coach education camps, it is very likely that for an athlete with this very example, meaning training only two to four times per week for a total of two to four hours per week, the high intensity training is actually more beneficial in terms of not only burning more calories, but also triggering better adaptation, improving performance more and faster.

But that's a different topic. Okay, so for this person, in the scenario I just described, it only really makes sense, or it makes a lot of sense, and it's actually possible to have every training session beside or except for the warm-up, warm-down, and the time in between the intervals, just have it a high-intense session, period.

Nothing else. Okay, and it will work. And what does it mean? If you take away the warm-up and the warm-down and the time in between, you will end up with approximately, approximately in this person, 50 to 60% of the time spent at high intensity. So far, far away from the 80/20 rule. Two to three-fold more percentage in terms of high intensity. That's one extreme. Let's take it to the other extreme.

Let's take an elite endurance athlete. Elite endurance athletes, either you go from swimming or triathlon or cycling, whatever, they train for approximately, as a ballpark number, 30 hours per week. If you think that's a bit too much or too low, you can do the same example with 33 hours or 25. It doesn't really matter.

Hear me out. In this case, 20% high intensity in the case of 30 hours would mean three hours of high intensity training. So again, we just mentioned that depleting the glycogen stores would basically take approximately 60 to 90 minutes. And to be clear, glycogen is the very fuel and the almost only fuel an athlete can use during this high intensity.

So that means that if you would put an athlete to six hours per week high-intense training, and let's say, for an example, say this athlete has one rest day per week, meaning the athlete would do one hour of high-intensity training every day, six days in a row. That does not work at all.

After day one, glycogen stores are almost depleted, meaning even with a high-carbohydrate diet, it's impossible to replenish completely until day two, meaning day two, likely this high intense interval session would already be needed to cut short. And day three is absolutely impossible. So 20% here also doesn't work.

In our first example, with a low volume recreational, hobby athlete, so to speak, it doesn't make sense because the athlete could train harder, actually can train hard every day. In the elite endurance athlete example, it's simply impossible. Besides, again, it's not advisable because it will not trigger the best adaptation likely for this kind of athlete.

It is, energetically speaking, just not possible. So that actually means the 80/20 rule doesn't really work for this guy. This elite athlete can have approximately, that's a rule of thumb, 90 minutes to two hours of high intense training. Not any different. The total number, if you think back of our hobby athlete, three to four times per week, half an hour net time at high intensity is also 90 minutes to two hours.

So the total hours of high intense interval training or high intensity work per week is limited, is ceiled somewhat in the ballpark of one and a half to two hours of really to have a meaningful training stimulus, what is energetically possible. So logically, think about it. If your total time at this high intensity training is ceiled at roughly maximum two hours per week, in a practical sense likely more like 90 minutes, then the percentage has to drop dramatically as your total training time goes up per week.

And that's what you see in reality in elite athletes. An elite athlete will only spend two to five percent at a maximum, two to five percent in high intensity training, because it's just not possible otherwise, given the whole training volume. And this 2% to 5% will come out as one and a half to two hours.

And in a hobby athlete, again, it will more be 40% to 60%. But this 40% to 60% will be approximately the same one and a half to two hours.

There was an interesting study which tells the same story about this example, but it goes a little deeper. In this specific training study, subjects were introduced to three different periods of training. One with what they called a moderate dose and one with what they would call like low dose and an excessive dose of high-intensity training.

And the moderate dose was 90 minutes approximately. So the very 90 minutes we just talked about. And the excessive dose, so on purpose doing more high intensity work, was two and a half hours. Not so much more than what I just explained, the maximum ceiling being really two hours per week. So two and a half hours compared to one and a half hour of accumulated time at high intensity led to a net loss in mitochondria capacity.

So mitochondria is the part of the muscle cell, or any cell, actually, that's responsible for your energy production. It is the very thing you are chasing in terms of adaptation of the muscle for endurance performance as well as for healthspan and lifespan. So what they've shown is that likely, they hypothesize likely because of increased mitochondria degradation, so losing mitochondria protein because of that high intensity.

What basically happened again is switching from 90 minutes per week accumulate high intensity time to two and a half hours, there was a loss in mitochondria capacity across the athlete. Again, telling the same story just from a different angle, not so much from the energetic level, however, it might be linked from a muscle adaptation level, losing mitochondria mass if the training volume accumulated time at high intensity is too high.

So bottom line is, what you want to do for your own training, or for the athletes that you coach, you want to look for the total time, not a percentage, the total time of minutes spent in the high intensity zone, net minutes. Look at that. Use that as a guideline. And then whatever the percentage that accounts for in the total training volume, either if it's 5% or 10 or 20 or 40 or 50%, doesn't really matter. So percentage is the outcome. It's not a metric you want to aim for.