Is Zone 2 60–70% of max heart rate or heart rate reserve?

What is the difference between %HRmax, Karvonen, and lactate-based Zone 2?

Three definitions, and only two of them are arithmetic. Percentage of max HR multiplies your max by 60–70%. Karvonen, also called heart rate reserve, takes 60–70% of the gap between your resting and max heart rate, then adds your resting rate back. Lactate-based Zone 2 drops percentages entirely. It puts the ceiling just below your first lactate threshold (LT1), which needs a lab to measure.

The first two share the digits 60–70% and share the name Zone 2. They do not share a denominator, so they do not produce the same range.

Why do different sources and devices give different Zone 2 heart rates?

Because the percentage gets published without the scale it belongs to. A page that says Zone 2 is 60–70% has said almost nothing until it says 60–70% of what, and most don't.

Mayo Clinic Press does both at once. Its zone 2 article defines the zone as 60% to 70% of maximum heart rate. It then tells readers to subtract resting heart rate from maximum, multiply by 0.6 and 0.7, and add resting heart rate back. That second procedure is heart rate reserve, not percentage of max, and the article never flags the switch. For a runner with a resting heart rate of 50 and a max of 190, the label and the arithmetic differ by about 20 BPM. Running magazines carry the same split across their zone 2 coverage.

Reusing one set of digits across both scales is a consumer-content habit, not a professional one. ACSM's intensity classifications assign each scale its own numbers.

Those are ACSM's categories for apparently healthy adults, published in its 2011 position stand. ACSM doesn't use the label "Zone 2" at all, and its moderate band isn't a Zone 2 definition. The point is narrower and useful: when a governing body maps intensity onto both scales, the numbers come out different, because the scales are different.

And beneath the labeling problem sits a physiological one: even a fixed percentage applied correctly lands somewhere different in each body. A 2025 study in Translational Sports Medicine compared ten Zone 2 definitions in the same 50 experienced cyclists and found that holding everyone at a fixed 72% of max heart rate left their actual metabolic intensity scattered: oxygen uptake varied between riders with a coefficient of variation of 24.7%, and cycling power 27.6%. The tight clustering only appeared when the anchor was metabolic: at markers like the first ventilatory threshold, heart rate varied with coefficients of variation between 6.0% and 10.8%. That's a cyclist finding, not a runner one, but the mechanism is the point: sources disagree about which percentage to publish, and the same percentage then means something different in your body than in the next runner's.

Why is the Zone 2 range my watch shows so low?

Because Garmin and Polar default to percentage of max HR, and that method produces the lower of the two Zone 2 ranges. For a runner with a resting heart rate of 50 and a max of 190, the %HRmax default gives 114–133 BPM where heart rate reserve gives 134–148. That's the setting talking, not your fitness.

Whoop applies the same 60–70% band to heart rate reserve instead. That's why its Zone 2 reads higher than a Garmin's for the same athlete. Neither device is malfunctioning. They ship different defaults.

Garmin's manuals document that supported watches can switch heart rate zones from %HRmax to %HRR. Some models also offer a percentage of lactate threshold heart rate. Changing that setting is usually the whole fix. If your easy runs feel absurdly slow at the number your watch gives you, check which method it's set to first.

Why is Zone 2 sometimes 60–70% and sometimes 70–80%?

Because two different things are being called Zone 2. Wearables and RunBeat use 60–70% by formula. The endurance-training register, where the podcast conversation about Zone 2 came from, describes it as roughly 70–80% of max heart rate. That higher band isn't a third formula. It describes work sitting just below the first lactate threshold.

A 2025 expert-panel commentary in the International Journal of Sports Physiology and Performance put 14 experts, working mainly in cycling, on the definition. They defined Zone 2 by threshold rather than by percentage, placing it just below LT1 or VT1. The heart rate they expected there was roughly 70–80% of max, with blood lactate around 1–2 mmol/L. Those figures describe what the intensity typically looks like.

The same paper shows how the label itself splits. In the three-zone laboratory model, LT1 divides zones 1 and 2 and LT2 divides zones 2 and 3, so "Zone 2" there means everything between the two thresholds. In the five-zone model, Zone 2 sits below LT1. Same words, harder training. Published models use anywhere from three to seven zones.

The practical read: 70–80% of max HR and 60–70% of heart rate reserve describe similar efforts. That's part of why heart rate reserve tends to match how a run actually feels.

Should I use max heart rate or heart rate reserve to set my zones?

Heart rate reserve. It's the method RunBeat uses, and it's the one that reconciles the three competing conventions: the 60–70% device band, the 70–80% endurance register, and the lactate-anchored definition. It also uses your resting heart rate, which percentage of max discards entirely. That lets it tell apart two runners with the same max and very different fitness.

We recommend heart rate reserve for its inputs, not for physiological accuracy. ACSM classifies moderate intensity as 40–59% of heart rate reserve but 64–76% of max HR, so percentage of max works fine when you use its own numbers. Those numbers just aren't 60–70%.

The honest case for heart rate reserve is narrower and still decisive. The one extra input it needs, your resting heart rate, is free to measure. Its output lands near what the threshold-anchored definitions describe. And runners on forums and in coaching write-ups consistently report that its targets match their perceived effort better than the %HRmax defaults do.

The formula is named for a 1957 study by Karvonen, Kentala, and Mustala. They prescribed intensity as a fraction of the range between resting and maximum heart rate. That study had six subjects. The zone tables came later.

Zone boundaries are conventions of a model, not constants of your body. Pick one method, apply it consistently, and judge it against how your runs feel.

RunBeat sets your zones by heart rate reserve by default, and Zone Training holds you inside the range by voice:

Zone Training in RunBeat RunBeat tells you to speed up or slow down to stay in zone, right over your music or podcast.

What max HR and resting HR do I plug into the formulas?

• Resting heart rate: measure on waking, before getting up, averaged over several days; the average your wearable reports is fine.
• Max heart rate: the highest reading from a genuinely maximal effort within the last year, a hard race finish or a max-effort field test.

A wearable-recorded max from training history works if the effort behind it was real. If you won't test, 220 minus age is the fallback, and it's the default your watch already uses. It's an estimate to start from, standing in until a tested max exists. Age-based formulas carry individual spread of roughly plus or minus 10–12 BPM at one standard deviation. The number describes a population, not you. Replace it with observed data when you have some.

Max HR feeds both the percentage-of-max formula and the heart rate reserve formula, so an error there moves every zone you calculate. Getting a real reading improves your zones whichever method you settle on.