How to set your heart-rate zones (and why 220 − age is wrong)

What zones are supposed to mark

Training zones are meant to follow real changes in your body, not round numbers. Two thresholds matter most:

• The first threshold (LT1 or VT1): where blood lactate, a by-product of burning carbohydrate, first rises above resting levels. Below it is easy running.
• The second threshold (LT2 or VT2): where lactate builds up faster than you can clear it. Above it, you tire within minutes.

A review of how to anchor zones found that the first threshold validly marks the boundary between moderate and heavy exercise. For the upper boundary, between heavy and severe, only critical power and critical speed did so reliably among the common methods. Percentages of maximum heart rate or of VO2max were weak anchors (Jamnick and colleagues, 2020). VO2max is the most oxygen your body can use per minute.

Why so weak? Because thresholds vary hugely between people. Across 100 people, the lactate threshold fell anywhere from 45% to 74% of VO2max (Iannetta and colleagues, 2020). A fixed percentage puts some runners in the right zone and others well outside it.

Why 220 − age is wrong

The best-known formula for maximum heart rate is 220 − age. It underestimates maximum heart rate in older adults. A better formula is 208 − 0.7 × age (Tanaka and colleagues, 2001).

But even the better formula is only an average. For any one person, age-predicted maximum heart rate has a standard error of about 11 beats per minute (Nes and colleagues, 2013). Your real maximum could easily be 10 or more beats away from the formula. Every zone built on it inherits that error.

For a 40-year-old, 220 − age gives 180. The Tanaka formula gives 180 too (208 − 28). At 60, they split: 160 versus 166. Either way, you could be well off.

The better order of methods

Here is the order the evidence supports, from best to worst:

1. A lab test that measures your thresholds directly, by blood lactate or breathing gases.
2. Critical speed from your own running. Critical speed marks the line between hard-but-sustainable running and severe running. You can estimate it from best efforts in normal GPS training data over 6–12 weeks, such as 400 m, 800 m and 5000 m, or from three all-out efforts lasting 2–15 minutes each.
3. Heart rate at tested thresholds, taken from a lab or field test.
4. The talk test or perceived effort.
5. An age formula, only if nothing else is available.

Critical speed works well in practice. In more than 25,000 runners, critical speed estimated from everyday training best efforts predicted marathon time to within 7.67% (Smyth & Muniz-Pumares, 2020).

The good news: the exact method may matter less than you fear. In a 2025 analysis that pooled many training trials, mixing different anchoring methods across trials did not change the results (Rosenblat and colleagues, 2025). What matters most is that easy running is truly easy. See how much of your running should be easy.

The talk test

The talk test is free and surprisingly good. Talk test and rated effort both track both thresholds (Bok and colleagues, 2022):

• Full conversation: below the first threshold. Easy.
• The point where talking first gets uncertain, at a rated effort of about 10–11 on the 6–20 Borg scale, marks the first threshold.
• Short phrases only, at a rated effort of about 13–15, marks the second threshold.
• Can’t talk: above it.

Use it to sanity-check zones from any other method. If your “easy” heart-rate zone leaves you unable to chat, your zones are probably set too high.

Formulas to skip

MAF “180 − age”. This popular formula for an aerobic heart rate is untested. Its author concedes it is not linked to the lactate threshold. Treat it as a rough heuristic at best.

Your watch’s threshold pace. In one validation, watch-estimated lactate-threshold heart rate was usable, but the threshold pace was overestimated by about 26% (Frontiers study, 2025). Use the heart rate as a starting estimate and ignore the pace.

Heart rate has limits too

Heart rate can misrepresent short, hard reps. In highly trained runners, 30-second reps gave less time near VO2max than 3-minute reps, yet showed more time at high heart rate (Fleckenstein and colleagues, 2024). For short intervals, go by pace or effort.

Sensors matter too. Chest straps measure heart rate within about 1–3%, while wrist sensors get worse at higher speeds and vary by model (OSU validation).

What we don’t know

• No trial shows that one zone method leads to faster marathons than another.
• The talk-test and effort cut-offs are averages. Individuals vary.
• Zone cut-offs based on critical speed are partly assumed. One proposed scheme puts easy running below about 82% of critical speed, but that boundary has not been tested.

Sources

• Jamnick et al. (2020). Review of methods for anchoring exercise intensity domains.
• Iannetta et al. (2020). Individual variation in the lactate threshold as a share of VO2max.
• Tanaka et al. (2001). Age-predicted maximal heart rate formula.
• Nes et al. (2013). Accuracy of age-predicted maximal heart rate.
• Smyth & Muniz-Pumares (2020). Critical speed from training data and marathon prediction in over 25,000 runners.
• Rosenblat et al. (2025). Individual-participant network meta-analysis of training intensity distribution.
• Bok et al. (2022). Talk test and perceived effort for finding ventilatory thresholds.
• Maffetone. The 180 formula.
• Frontiers study (2025). Validation of watch-estimated lactate threshold.
• Fleckenstein et al. (2024). Time near VO2max in short vs long intervals in highly trained runners.
• OSU validation. Garmin and Polar heart-rate accuracy.