PX7 Training Method · 4 min read · 2026-04-17
Why 80/20 beats the grey zone
Most recreational runners spend half their week at an intensity that is too hard to recover from and too easy to drive adaptation. The PX7 Training Method refuses that zone on purpose.
Look at the training logs of elite endurance runners long enough and a pattern emerges that surprises most recreational athletes: the volume is enormous, and almost all of it is easy. Hard work happens, but it's sharp, measured, and rarely spills into the moderate middle. The Norwegian endurance tradition — middle-distance runners, cross-country skiers, biathletes — is the clearest public expression of this pattern, and it's the tradition the PX7 Training Method is built on.
The shape of polarised training
Polarised training means two things. First, the distribution: roughly eighty percent of sessions sit at low intensity, and the remaining twenty percent sit at or just below lactate threshold, with occasional VO₂max work above it. Second, and more important: the zone in the middle — what runners call "comfortably hard" — is avoided deliberately.
That middle zone is where a disproportionate share of recreational training lands, because it feels productive. You come home with effort in your legs. But physiologically it is the worst of both worlds: hard enough to accumulate fatigue, not hard enough to drive the adaptations that actually raise your ceiling.
What each end of the spectrum is for
Easy running, truly easy running, is how you build the plumbing. Low-intensity volume grows mitochondrial density, capillary beds, fat oxidation, and stroke volume — the slow, boring, durable adaptations that every endurance performance is downstream of. Nothing about this work feels impressive while you're doing it. It is, however, what allows you to tolerate and recover from the hard work that matters.
The hard work is threshold and above. Threshold intervals teach your body to clear lactate at higher and higher intensities. VO₂max intervals push your maximum oxygen uptake ceiling. Both are expensive to recover from, which is why the elite pattern only uses a little of them — and why the middle zone steals that recovery without paying it back.
How PX7 Training implements the rule
We take the rule seriously enough to build the interface around it. Zones Z1 and Z2 are the easy backbone of every week. Threshold work sits in Z3; VO₂max in Z4; short neuromuscular work in Z5. Two narrow bands on either side of threshold — NOX (88–93%, below threshold) and NOY (101–102%, just above threshold) — are labelled explicitly as avoid. NOX is the grey zone unsupervised easy runs drift into. NOY is the narrow gap between threshold and VO₂max that keeps interval work cleanly on one side or the other. You can see both, but the generator won't place sessions there.
It sounds rigid. In practice it's liberating. Your easy runs are allowed to be slow. Your hard runs are allowed to be hard. And the dashboard will tell you, over time, whether your week looks like the pattern elite runners actually follow.
Written by Jørgen Larsen for PX7 Training.