I am often asked if the 80/20 rule of intensity balance applies to athletes who train at very low volumes. It’s a fair question. We know that low-intensity exercise doesn’t do a lot of good in small amounts, whereas high-intensity exercise does. It is plausible therefore that, below a certain volume threshold, doing less than 80 percent of one’s training at low intensity will yield better results than sticking to the 80/20 rule.

A new study by Luca Festa of the University of Verona and colleagues addresses this question—sort of. The subjects were recreational runners with at least four years of experience. For eight weeks, half of them followed a “polarized” training program in which 77 percent of training was done at low intensity, 3 percent at moderate intensity, and 20 percent at high intensity, while the other half maintained a 40/50/10 intensity split (“focused endurance training”). Volume was adjusted to ensure that the total training load (intensity and volume combined) was equal for the two groups. This required runners in the polarized group to run slightly more than runners in the focused endurance group, though volume was quite low in both groups, averaging out to 3.73 hours per week and 3.1 hours per week, respectively.

Physiological and performance measures were taken on all of the subjects before and immediately after the eight-week training intervention. The table below summarizes the results.

As you can see, they’re kind of a mixed bag. The polarized group saw bigger improvements in body composition, VO₂max, and (what is arguably the only result that matters) time-trial performance, while the focused endurance group experienced bigger gains in running economy and velocity at VO₂max. None of these differences was judged to be statistically significantly, however, so Festa’s team concluded that “Focused Endurance Training obtains similar improvements [as] Polarized Endurance Training[,] saving 17% of training time in recreational runners.”

There you have it: 80/20 training is a waste of time. You get equal results in less time by doing half of your training at moderate intensity, which is precisely the opposite of what 80/20 advocates like me tell athletes not to do.

But wait—there’s another interpretation. Remember the commonly asked question I mentioned at the top of this article? We started out with the premise that it is likely that, below a certain threshold of training volume, an 80/20 intensity balance might not yield optimal fitness benefits. The results of Festa’s study suggest that this threshold is very low indeed, if indeed it exists at all. Members of the polarized group and the focused endurance group ran just 32 minutes and 27 minutes per day, respectively, during the eight-week study period, and improved by roughly equal amounts. So it’s safe to say that you would have to run less than 25 minutes a day, on average, for a more intense training approach to possibly produce better results than the 80/20 method, emphasis on “possibly.”

It’s also worth drawing attention to the fact that the only performance test included in Festa’s study was a 2 km time trial. That’s pretty short. Why 2 km? Because Festa and his colleagues wanted to set up the focused endurance group for success, that’s why! Clearly, a short performance test was going to give the group doing shorter runs the best chance of equaling the improvement of the other group. Even then, though, the polarized group improved slightly more. And although the difference was statistically significant, meaning it could have happened by chance, I’d be willing to bet that if this same experiment were rerun 100 times, the polarized group would improve more with a frequency that exceeded chance, hinting at the beginning of a trend that would only grow as the distance of performance tests increased.

Furthermore, although Festa’s study itself was quite short, its brevity was appropriate in the sense that it doesn’t take long for a training program of such low volume to yield the full measure of its potential benefits. In other words, had the experiment lasted longer, it’s unlikely that either group would have improved much more. But suppose you were to actually follow one of the two programs involved in this study, getting whatever benefit you could squeeze out of it in 8-10 weeks, and then decided that you wanted to improve more going forward.

Here’s what would happen: If you were on the focused endurance plan and you proceeded by gradually increasing the volume of training you did at the same 40/50/10 intensity ratio, you would gain fitness at a gradually decreasing rate for a little while before reaching a point of negative returns at a still fairly modest volume level. That’s because any training done above the first ventilatory threshold—whether moderately intense or highly intense—is significantly more stressful to the body than training done below the VT₁, and on this program you’re doing 60 percent of your total running above that threshold. Festa’s team collected data on perceived effort from their subjects but did not report it, and again, I’d be willing to bet that members of the focused endurance group perceived their training to be harder than members of the polarized group perceived their training to be, even though mathematically their training loads were equal.

But if instead you went through the same process on the 80/20 program, you would continue to improve for a very long time, albeit at a diminishing rate, not reaching the point of negative returns until you’re doing a ton of running. And that’s because training below the first ventilatory threshold is so gentle on the body that even the average athlete can handle (and benefit from) massive amounts of it. I would only add that, whereas in this study almost all of the 20 percent of training done above the VT₁ was done at high intensity, a runner training at ever-increasing volumes would be wise to gradually shift minutes from the high-intensity bucket to the moderate-intensity bucket as volume grew.

Festa and his colleagues admit that it is a well-established fact that an 80/20 intensity balance provides the best possible results for athletes who train a lot, writing, “several studies have shown that it allows them to achieve greater improvements in performance,” and that “this distribution is necessary for athletes who perform a large volume of training, to prevent overtraining or steady state of performance.” What this new study shows is that the 80/20 approach is also at least as effective as a more intense training approach at a very low training volume of around 30 minutes a day. In other words, the title of this article is a joke.