How Do You Actually Find Your Zone 2?

Every Zone 2 app, including ours, starts by asking for a heart-rate range. Most people fill it in with a formula: 220 minus their age, then 60–70% of that. It feels scientific because it has numbers in it. But Zone 2 isn't defined by a percentage. It's defined by what's happening inside your body, and the point where that changes sits in a different place for different people.

So we went back to the research to answer three questions. What is Zone 2, physiologically? How well do the popular shortcuts find it? And what can a rider with a smart trainer and a heart-rate strap, but no lab and no lactate meter, actually do to find their own?

1What Zone 2 actually is

Part of the confusion is that "Zone 2" means different things in different systems. In the three-zone model used in most endurance research, everything below the first threshold is Zone 1, the easy zone^[2]. In the five-zone models used by cycling apps and coaches, that same easy territory is split in two, and "Zone 2" is its upper half. When people argue about Zone 2, they're often using different maps.

In 2025, a panel of 14 sport scientists and professional coaches tried to settle it. Their consensus was that Zone 2 training should be done at intensities immediately below the first lactate or ventilatory threshold^[1]. That threshold goes by several names (LT1, VT1, the aerobic threshold), but it describes one transition:

• Lactate in the blood stays near resting levels at easy intensities. At the first lactate threshold, it begins to rise above that baseline.
• Breathing tracks oxygen use at easy intensities. At the first ventilatory threshold, it starts to increase faster than oxygen use, which is why talking gets harder.

Below this point, the work is sustainable for hours and recovery is quick. Above it, fatigue builds faster and recovery takes longer. That's the whole reason the zone matters: you want as much aerobic stimulus as possible without crossing into the territory that costs you recovery.

You'll also hear Zone 2 described as the point of maximum fat burning, an idea popularised by Iñigo San-Millán's work^[3]. The two aren't the same. In 50 trained cyclists, peak fat burning happened at an intensity about a quarter lower than the first ventilatory threshold^[6]. For a rider trying to build endurance, the threshold is the more useful anchor, and it's the one the expert consensus uses.

2How a lab finds it

In a lab, you ride a test that gets progressively harder while the lab measures your breathing gases, your blood lactate, or both. The first threshold is read off the data where the curve bends.

Even this "gold standard" isn't one thing. A review of lactate threshold methods found 25 different ways of defining a lactate threshold. Some use a fixed concentration, others the first rise above baseline, others the shape of the curve^[4]. Test protocols vary too, and they change the answer. A later critique of intensity-prescription methods concluded that the first lactate threshold and the ventilatory and gas-exchange thresholds do have real evidence behind them as the boundary between easy and moderate-to-hard exercise^[5]. That's the boundary that matters for Zone 2.

So the lab gives the best available answer, but not a perfectly sharp one. Keep that in mind when you judge the home methods below. The target is a region a few beats wide, not a single magic number.

3Why the formulas miss

Problem one: your maximum heart rate

Most formulas start from maximum heart rate, and most people estimate that from their age. "220 minus age" wasn't derived from a study at all. When Robergs and Landwehr traced its history, they found it came from an observation based on about 11 earlier sources, not original research, and that age-based predictions of maximum heart rate typically have errors of 7–11 beats a minute^[9]. A better equation, 208 − 0.7 × age, fits population averages more closely, especially in older adults^[10]. But a better average doesn't fix the spread between individuals. Two 45-year-olds can easily have maximums 20 beats apart.

Problem two: the threshold isn't at a fixed percentage

Even if you know your true maximum, the threshold doesn't sit at the same percentage of it for everyone. In a study of 100 men and women, Iannetta and colleagues measured each person's maximum heart rate and first lactate threshold directly. The threshold fell anywhere from 60% to 90% of maximum heart rate. Prescriptions based on fixed percentages, they concluded, don't control the metabolic stimulus adequately^[7]. Percentages of VO₂max are no better. At the same 60% of VO₂max, blood lactate ranged from 0.7 to 5.6 mmol/L between individuals: from very easy for some people to well above threshold for others^[8].

Problem three: the popular numbers are low for trained cyclists

The most relevant study for our readers is Meixner and colleagues' 2025 lab work in 50 trained cyclists, men and women. Their first ventilatory threshold averaged 81% of maximum heart rate (± 4 percentage points)^[6]. An older cycling study found almost the same figure, 82%^[11]. The widely quoted 60–70% of maximum finishes more than ten points below that average.

That includes our own default. JustZone2 starts with a Zone 2 of 59–78% of maximum and aims for the upper part of it. That's deliberately cautious: riding a little too easy costs you some stimulus, while riding a little too hard costs you recovery. But for an average trained cyclist it sits several beats below their real threshold. The defaults are a starting point. The rest of this post is about replacing them with your own numbers.

What about MAF (180 minus age)?

Phil Maffetone's formula takes 180 minus your age and then adjusts it by up to 10 beats for health and training history^[19]. It has a big following, and the adjustments are a sensible nudge towards caution. But we couldn't find any peer-reviewed study validating it against measured lactate or ventilatory thresholds, and the formula's own documentation doesn't cite one. Because it ignores maximum heart rate, it inherits the same person-to-person spread as the age formulas, possibly more. Treat it as a cautious rule of thumb, not a measurement.

And heart rate reserve (Karvonen)?

Using heart rate reserve (maximum minus resting) builds in your resting rate, which helps a little. In a cycling test, the ventilatory threshold fell at about 74% of heart rate reserve on average^[11]. But it's still a fixed percentage of an uncertain maximum, with the same spread between individuals.

4What you can do without a lab

The talk test: the best free method

The talk test sounds too simple to be science, but it has been studied properly. Ride progressively harder and, at the end of each stage, say a standard passage aloud. Then ask yourself one question: could I speak comfortably?

In Persinger and colleagues' study, people did this on both a treadmill and a cycle ergometer while their breathing gases were measured. The stage where speech first became not quite comfortable (the "equivocal" stage) matched the ventilatory threshold almost exactly on both. Stages where speech was clearly uncomfortable were consistently above it^[11]. A follow-up by Foster and colleagues then moved people's thresholds deliberately, down by giving blood and up by training. The talk test tracked the threshold both ways^[12].

Two details from that follow-up shape how you should run the test. First, when the intensity was just above threshold, it often took more than two minutes for talking to become uncomfortable, so short stages will overestimate your threshold. Second, errors leaned towards people passing the test when they were actually above threshold^[12]. The fix for both is to use longer stages and to set the top of Zone 2 at the last stage that was fully comfortable, not the uncertain one.

Measure your maximum, don't predict it

If you want to use percentages as a cross-check, use a maximum you've actually seen on a bike, such as the highest reading at the end of an all-out climb or race finish, rather than one predicted from your age. Heart rate reaches different maximums in different sports, so a running maximum isn't a good guide for cycling. If you're older, untrained or have any heart condition, don't go looking for your maximum without medical advice. The talk test doesn't need it.

HRV thresholds (DFA a1): promising, not yet precise

A newer method reads the threshold from the pattern of beat-to-beat variation in your heart rate, using a measure called DFA alpha1. As intensity rises, the value falls, and in the first study of the method, the point where it crossed 0.75 agreed closely with the ventilatory threshold in 15 runners^[13]. A 2024 meta-analysis found strong agreement on average across studies, but very wide differences between them^[14].

The individual results are the problem. In one study, the standard 0.75 cut-off put the threshold about 15 beats a minute too high on average. A personalised cut-off worked better^[15]. In a 2026 study of 21 trained cyclists using a 4-minute step test, it was 17 beats too low on average compared with the ventilatory threshold, with limits of agreement of ± 24 beats. The authors concluded it wasn't suitable for setting an individual's threshold with that protocol^[16]. The method also needs accurate beat-to-beat data: the studies used chest straps or ECG. It's worth watching, and interesting as a second opinion, but we wouldn't set your zones from it alone yet.

The drift check: a sanity test, not a measurement

Many coaches use a "heart-rate drift" or "decoupling" test: ride for an hour at a steady power, and compare your average heart rate in the second half with the first. If it rises by less than about 5%, the power was at or below your aerobic threshold. If it climbs well beyond that, you were probably above it.

The physiology behind it is real. During long exercise, heart rate drifts upwards while the heart's stroke volume falls^[17]. But we found no peer-reviewed study validating the 5% rule against a lab threshold. Heat, dehydration and fatigue also increase drift, which makes this a test of the conditions as much as of the intensity. Use it to confirm a number you found another way, in a cool room with a fan, not as the way to find it.

Lactate meters: possible, but not the answer to everything

Portable lactate meters let you do a home version of the lab test with finger-prick samples. They can work well in experienced hands, but a single reading is noisy, and technique matters. And as the 25 definitions above show, you still have to decide which threshold concept to use^[4]. For most riders, the extra precision over a careful talk test probably isn't worth the cost and fuss.

Method	Our verdict
220 − age, then %	Starting guess only. Errors of 7–11 bpm in the maximum, plus a threshold anywhere from 60–90% of it.
MAF (180 − age)	Cautious rule of thumb. No published validation that we could find.
Talk test	Best free method. Well validated against the ventilatory threshold, on a bike too.
HRV (DFA a1)	Promising. Good on average, too variable individually to rely on alone.
Drift check	Useful confirmation. Not validated as a way to find the threshold.
Lab test	Best available, if you can get one. Still a few beats of uncertainty.

5A step test you can do on your trainer

A smart trainer in ERG mode is almost ideal for this. It holds each stage at an exact power, so the only thing changing is you. Here's the protocol we'd suggest, built on the talk-test studies above.

1. Pick a good day. Rested, not the day after a hard session, in a cool room with a fan, and with your usual caffeine. Heat and fatigue both push heart rate up.
2. Warm up for 10 minutes at a power that feels very easy.
3. Start the steps well below where you think Zone 2 is. If you know your FTP, around half of it is a reasonable start. Otherwise, pick a power where breathing through your nose is effortless.
4. Hold each step for 4 minutes, then add 10–15 W (lighter riders towards 10). Longer steps matter: it can take over two minutes above threshold before talking gets hard^[12].
5. At about 3½ minutes into each step, note your heart rate. Then say something aloud for 20–30 seconds, the same passage each time. Anything you know by heart will do.
6. Rate it honestly: yes (comfortable), not sure, or no. Stop after your first "no". You don't need to go anywhere near your maximum.
7. The top of your Zone 2 is the heart rate on your last clear "yes". The "not sure" step is roughly your threshold.
8. Repeat it another day. If the two results are within a few beats, trust them. If not, do a third.

Then confirm it. Ride for an hour just below that heart rate, in the same cool conditions. If you can hold a conversation throughout and the heart rate stays steady at a steady power, you've found it. If it climbs steadily, move the top down by a few beats.

6Keeping it right

Retest every couple of months, or after a big change in fitness, illness or a long break. Training moves your threshold. In Foster's study, the talk test moved with it^[12].

Expect day-to-day wobble. Heart rate at the same power shifts with fatigue, heat, hydration and sleep. That's why heart-rate measures are useful for monitoring training, and why small changes have to be read against their normal variation^[18]. A heart-rate-controlled ride handles this automatically: on a hot or tired day, the power drops to keep your heart rate in place. That's the point of training by heart rate, not a sign that something's wrong.

Trust your breathing over the number. If you're at your Zone 2 heart rate and can't talk in full sentences, the number is wrong for today, or wrong altogether. The talk test is the check you always carry with you.

Don't over-engineer the bottom of the zone. The benefits of Zone 2 aren't unique to one precise intensity. The same expert panel expected similar adaptations slightly above and below it^[1]. What matters most is not crossing the threshold, which is why the top boundary deserves your care.

7Limitations

The talk-test studies are small (16 people in the key comparison) and include few older or untrained riders. The cycling threshold figures come from trained cyclists, and less-trained people may sit elsewhere. Iannetta's 60–90% spread suggests that everyone should test rather than assume. The lab methods we compare against disagree with each other by a few beats. We found no study validating the full home protocol above as a package: it's our synthesis of the talk-test evidence, with the stage length and the "last clear yes" rule taken from that evidence. Nothing here is medical advice. If you have a heart condition or take medication that affects heart rate, such as beta blockers, speak to your doctor before testing or training by heart rate.

References

1. Sitko S, Artetxe X, Bonnevie-Svendsen M, et al. What is "Zone 2 training"?: experts' viewpoint on definition, training methods, and expected adaptations. Int J Sports Physiol Perform. 2025;20:1614–1617.
2. Seiler S. What is best practice for training intensity and duration distribution in endurance athletes? Int J Sports Physiol Perform. 2010;5:276–291.
3. San-Millán I, Brooks GA. Assessment of metabolic flexibility by means of measuring blood lactate, fat, and carbohydrate oxidation responses to exercise in professional endurance athletes and less-fit individuals. Sports Med. 2018;48:467–479.
4. Faude O, Kindermann W, Meyer T. Lactate threshold concepts: how valid are they? Sports Med. 2009;39:469–490.
5. Jamnick NA, Pettitt RW, Granata C, Pyne DB, Bishop DJ. An examination and critique of current methods to determine exercise intensity. Sports Med. 2020;50:1729–1756.
6. Meixner B, Filipas L, Holmberg HC, Sperlich B. Zone 2 intensity: a critical comparison of individual variability in different submaximal exercise intensity boundaries. Transl Sports Med. 2025;2025:2008291.
7. Iannetta D, Inglis EC, Mattu AT, et al. A critical evaluation of current methods for exercise prescription in women and men. Med Sci Sports Exerc. 2020;52:466–473.
8. Scharhag-Rosenberger F, Meyer T, Gässler N, Faude O, Kindermann W. Exercise at given percentages of VO₂max: heterogeneous metabolic responses between individuals. J Sci Med Sport. 2010;13:74–79.
9. Robergs RA, Landwehr R. The surprising history of the "HRmax = 220 − age" equation. J Exerc Physiol Online. 2002;5(2):1–10.
10. Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol. 2001;37:153–156.
11. Persinger R, Foster C, Gibson M, Fater DC, Porcari JP. Consistency of the talk test for exercise prescription. Med Sci Sports Exerc. 2004;36:1632–1636.
12. Foster C, Porcari JP, Anderson J, et al. The talk test as a marker of exercise training intensity. J Cardiopulm Rehabil Prev. 2008;28:24–30.
13. Rogers B, Giles D, Draper N, Hoos O, Gronwald T. A new detection method defining the aerobic threshold for endurance exercise and training prescription based on fractal correlation properties of heart rate variability. Front Physiol. 2021;11:596567.
14. Tanner V, Millet GP, Bourdillon N. Agreement between heart rate variability-derived vs. ventilatory and lactate thresholds: a systematic review with meta-analyses. Sports Med Open. 2024;10:109.
15. Rogers B, Fleitas-Paniagua PR, Murias JM. Improving the agreement between the first heart-rate-variability threshold and the gas-exchange threshold. Int J Sports Physiol Perform. 2024;19:1434–1443.
16. Olieslagers A, Müller-Jabusch Y, Vancoillie M, Delen E, de Beukelaar T. Agreement between heart rate variability-derived and lactate/ventilatory thresholds during a 4-min stepwise incremental cycling test in male adults. Physiol Rep. 2026;14(4):e70777.
17. Coyle EF, González-Alonso J. Cardiovascular drift during prolonged exercise: new perspectives. Exerc Sport Sci Rev. 2001;29:88–92.
18. Buchheit M. Monitoring training status with HR measures: do all roads lead to Rome? Front Physiol. 2014;5:73.
19. Maffetone P. The MAF 180 Formula: heart-rate monitoring for real aerobic training. philmaffetone.com/180-formula (accessed September 2026).