Buzz
Many runners swear by the 80/20 rule to structure their workouts—but it's unrelated to the Pareto principle of the same name. Let’s dive into the origins of the 80/20 method, how to put it into practice, and when it’s a good (or not-so-good) idea to follow this approach in your training.
What exactly is the 80/20 rule in running?
In a nutshell, it means 80% of your running should be low-intensity, and just 20% should be at moderate or high intensity. For recreational runners (like us), we often end up running at a 50/50 split. The 80/20 rule encourages us to slow down some of our faster runs and find a healthier balance in our training.
The concept of the 80/20 rule was popularized by Matt Fitzgerald in his 2014 book, 80/20 Running. Fitzgerald based his approach on the work of Stephen Seiler, who found that top athletes in endurance sports like running, cycling, and cross-country skiing spent around 80% of their training time at lower intensities than they would during actual races. In essence, to train your body to be fast, you must log a lot of slow miles. This idea aligns with 'polarized training,' which advocates sticking to the extremes—either training very easy or very hard, and avoiding the middle ground.
It’s important to understand that the 80/20 rule here refers strictly to the breakdown of your training: 80% easy, 20% hard. This is not the Pareto principle, which suggests that 80% of your outcomes come from 20% of your efforts (e.g., 80% of sales from 20% of customers, or 80% of your needs fulfilled by just 20% of your possessions). In running, the 'result' is your race performance, and the idea is to divide your training time in the ratio of 80% easy and 20% hard for optimal results, according to Fitzgerald and Seiler.
What counts as low intensity for the 80%?
If you’ve been following the 'zone 2' trend, you might think that you should aim for zone 2 (roughly 60-70% of your maximum heart rate) for 80% of your training. And you know what? That’s pretty much on point. Go ahead and use that as a guideline.
However, the definitions used in scientific studies often go beyond heart rate alone. Some use metrics that are harder to measure on your own—good luck trying to keep your blood lactate below 2 millimoles per liter.
A more practical approach—and one that is supported by research—is to use VT1, the 'first ventilatory threshold.' This is essentially what seasoned runners refer to as the 'talk test.' If you can chat without pausing to catch your breath mid-sentence, you’re below VT1. This should be the intensity of 80% of your training sessions.
For those of you who crave more data, Fitzgerald mentions in his book that this threshold usually falls between 77% and 79% of elite athletes' max heart rate. The exact figure can vary for each person, and heart rate readings are never completely reliable due to factors like heat and stress. But as a reference, for me, 77% of my tested max heart rate comes out to around 153, which happens to align closely with my easy pace. I aim for the low 150's during my easy runs.
By putting all this together, it turns out we can go a little above 'zone 2' and still maintain the correct intensity for the 80% portion of your 80/20 training—provided it still feels easy. If you'd like, you can customize your zones on your running watch to cap out around 77%, or even set that as the top of zone 3, rather than zone 2.
How to implement the 80/20 rule in your training
Before we break down how to structure our training, we first need to determine how we’ll measure it. Should we consider easy runs as 80% of our training sessions? 80% of our total miles? Or 80% of our overall training time?
In his book, Fitzgerald calculated the minutes spent at easy, moderate, and hard intensities. However, for interval training, he counted both the intervals and the recovery time as part of the harder intensity work. (The cooldown after the intervals, though, would be considered low intensity.)
You can apply the same method. It’s also useful to think about it in terms of miles or sessions. For instance, if you run one hard session for every four easy ones, you’re still following the 80/20 approach (assuming the distances for each are similar).
How crucial is it to stick to the 80/20 rule?
While it's called a 'rule,' this isn’t something you absolutely must follow. It’s simply a training method that mirrors the practices of many elite athletes. Research has shown that recreational runners can benefit from it, but that doesn’t mean it’s the only viable way to train.
Seidler, the researcher, even told Fitzgerald, the author, that if he only had two training sessions a week, he’d combine harder and easier efforts in both sessions. Studies on competitive recreational runners found that a 77/23 split and a 46/54 split both led to modest improvements in 10K times, with no significant statistical difference between the two. However, the runners in the study had 10K times (6.2 miles) under 40 minutes to begin with, meaning they were already quite fast compared to many beginner runners.
At the same time, there is a wealth of research suggesting that recreational runners can see improvements with nearly any training approach, and that increasing weekly mileage is key to boosting both fitness and race performance.
The key takeaway
If you’re a runner still working on improving (which applies to many beginners, intermediates, and casual runners), you don’t necessarily need to slow down 80% of your runs to a crawl. Any conversational pace that feels comfortable to you will work, even if your watch shows that you're in zone 3. Since increasing your mileage is typically part of becoming a better runner, it may be more effective to focus on adding easy miles rather than trying to make your hard runs easier.
