Zone 2: why “180 minus age” lies and how to find your easy pace

“Just run slow” — that's how Zone 2 usually gets explained. It sounds simple, until it turns out that some amateurs run their “Zone 2” noticeably faster than they should, others slower, and the argument over exactly where it lies has dragged on for years. In 2025 several studies showed at once: it's not about laziness or willpower. It's about the formulas we've grown used to trusting.

What Zone 2 actually is

In 2025 a panel of 14 sports scientists and practicing coaches published a consensus in International Journal of Sports Physiology and Performance. The conclusion: Zone 2 is best performed at an intensity just below the first lactate or ventilatory threshold (LT1/VT1).

What does that mean in practice? Below this threshold the body still covers most of its energy needs from fat, and blood lactate stays low and stable (a rough benchmark — around < 2 mmol/l). This is that “conversational” pace: there's effort, but it's steady and comfortable.

Why does it matter? Experts expect Zone 2 to deliver a broad set of adaptations — both peripheral and central: growth in the number and quality of mitochondria, development of the capillary network, a stronger aerobic base. You can track progress indirectly: over time, at the same power, lactate drops, and your heart rate and perceived effort (RPE) at a familiar load fall. Your durability grows too — the ability to hold power toward the end of a long effort.

Why heart-rate formulas lie

The popular formulas — “180 minus age” (the MAF method) or “60–70% of (220 − age)” — rest on a single assumption: that everyone's first threshold sits at the same percentage of heart rate. It doesn't.

Work by Meixner and colleagues (Translational Sports Medicine, 2025) tested 50 experienced cyclists and compared different ways of setting Zone 2. The spread between people turned out to be enormous: the coefficient of variation for Zone 2 markers ranged from 6% to 29%. Even heart-rate percentages, which had the lowest variability (around 6–7%), are deceptive: a difference of just 5% in heart rate is roughly 10 beats per minute, and that's enough to drift into a completely different zone. For power at a fixed lactate, the spread reached 29%.

The authors' conclusion is blunt: fixed percentages of maximum heart rate reflect real metabolism poorly, while personal reference points based on VT1 and FatMax are more accurate. Add to that the fact that even your formula-based “maximum heart rate” can differ from your true one by a dozen or two beats — and the neat number on your watch turns into a lottery.

How to find your Zone 2 without a lab:

The talk test. If you can speak in full sentences, you're in the zone. Start swallowing words or struggling to sing — ease off the pace.
“Nose breathing.” Crude but workable: if you can run while breathing through your nose alone, you're almost certainly below the threshold.
Perceived effort. About 2–3 out of 10. The thought “I could keep this up for hours” is a good sign.
Heart rate as a hint, not a law. Take a formula as a starting point, but double-check with the talk test. Hard to chat — slow down, even if your heart rate is “in the zone.”

How much Zone 2 you actually need

From this grows the polarized 80/20 model: about 80% of the time easy, about 20% hard. For elites doing 15–25 h/week it works great: the volume is huge, and the lion's share simply has to be easy, otherwise there's no recovering.

But honestly: if your budget is 3–5 h/week, blindly pouring 80% into easy isn't always optimal. With low volume the overall training stimulus is small as it is, and handing almost all of it to Zone 2 means shortchanging intensity. It makes more sense to keep 1 quality session (intervals or tempo) per week and hold the rest genuinely easy. The larger the volume gets (roughly > 8 h/week), the more the easy share grows and the closer you get to the “classic” 80/20.

A common mistake is the “gray zone”: constantly running a touch faster than Zone 2. Not quite hard, but not quite easy either. The result: easy sessions aren't easy enough to build a base and recover, while hard ones aren't hard enough to deliver a sharp stimulus. Neither fish nor fowl.

Limitations

Any formula is a starting point, not the truth. The gold standard is a lactate test or gas analysis; at an everyday level the talk test replaces it.
Between-individual variability is real: your threshold may not sit where your same-age neighbor's does.
Meixner's data come from cyclists; runners' heart rate at the same effort is usually higher, so the zones don't transfer one-to-one.
The “fat-burning zone” isn't about magical weight loss. Yes, in Zone 2 fat's share as fuel is highest, but weight comes down through overall energy expenditure and diet, not a single pace.

The bottom line

Zone 2 is below the first threshold (LT1/VT1), a “conversational” pace, not a specific number on your watch.
Heart-rate formulas lie: the spread of markers between people ranges from 6% to 29%, and 5% of heart rate is already ~10 bpm.
Set your zone by feel: the talk test, nose breathing, RPE 2–3/10. Heart rate only as a guide, with a caveat.
Budget decides: at 3–5 h/week don't copy the elite 80/20 — keep one quality session and make the rest truly easy.
Avoid the “gray zone” — the eternal “a touch faster than easy.” Easy should be easy.

Sources: Sitko S., Artetxe X. et al. “What Is Zone 2 Training?: Experts' Viewpoint on Definition, Training Methods, and Expected Adaptations”. International Journal of Sports Physiology and Performance, 2025;20(11):1614. https://doi.org/10.1123/ijspp.2024-0303 — Meixner B., Filipas L., Holmberg H.-C., Sperlich B. “Zone 2 Intensity: A Critical Comparison of Individual Variability in Different Submaximal Exercise Intensity Boundaries”. Translational Sports Medicine, 2025. https://doi.org/10.1155/tsm2/2008291