What is zone 2 running?
Zone 2 is the low end of a heart-rate training scale, an effort you can hold while still speaking in full sentences. Under the 5-zone model Garmin publishes, it sits at roughly 60 to 70% of your maximum heart rate. In the field, the talk test works as a stand-in: if your breathing stays conversational, you're close. In a lab, physiologist Inigo San Millan defines zone 2 by blood lactate, roughly 1.5 to 2.0 mmol/L. Heart-rate percentage, the talk test, and lab lactate are three separate ways of finding the same target, and a heart-rate-formula estimate is rougher than a lab test.
Zone 2 shows up on running watches and in coaching plans, but the exact number behind it depends on which definition is doing the work, and getting that wrong in either direction, running it too fast or fixating on the exact display number, undercuts the point of training there at all. Below is the 5-zone heart-rate model one major watch brand publishes, what the research behind low-intensity training actually measured, and how to find your own zone 2 without a lab.
The 5-zone heart rate model
Garmin's own guide to training by heart rate zones splits effort into five zones by percentage of maximum heart rate. Zone 2 sits at 60 to 70%, a zone Garmin describes as helping cardiovascular training and recovery.
| Zone | % of max heart rate | Garmin's label |
|---|---|---|
| Zone 1 | 50-60% | Warm up |
| Zone 2 | 60-70% | Easy |
| Zone 3 | 70-80% | Aerobic |
| Zone 4 | 80-90% | Threshold |
| Zone 5 | 90-100% | Maximum |
Source: Garmin, "How You Can Train by Heart Rate Zones Using Garmin." Other GPS-watch platforms publish their own five-zone scales built the same way; the exact cut points can shift a little depending on the brand and on which maximum-heart-rate number feeds the calculation.
Why low-intensity running gets attention
Norwegian exercise physiologist Stephen Seiler has studied what elite endurance athletes actually do in training, as opposed to what a plan says they should do. In a 2006 study with Espen Kjerland, published in Scandinavian Journal of Medicine & Science in Sports, Seiler and Kjerland tracked 384 training sessions over 32 consecutive days in nationally competitive junior cross-country skiers and found roughly 75% of sessions stayed below the skiers' lactate threshold zone, with 15 to 20% well above it and little time spent in between. That study's population was junior cross-country skiers.
For running specifically, a 2015 review by Thomas Stoggl and Billy Sperlich in Frontiers in Physiology, covering training logs across running, cycling, rowing, cross-country skiing and swimming, reported elite Kenyan distance runners training at low intensity around 84% of the time, and top marathon runners around 78% in the phase before a race.
Whether that distribution causes better performance, separate from just describing what fast athletes already do, is a different question. A 2024 systematic review by Henrik Lyngstad Nost, Morten Andreas Aune and Roland van den Tillaar in the journal Sports included 14 training studies, 10 of which measured VO2max or VO2peak; 8 of those 10 showed improvement under a polarized, low-intensity-heavy plan, 5 of them statistically significant, with effect sizes the review describes as varying from trivial to large. From that evidence, the review's own recommendation was a distribution of roughly 75 to 85% low-intensity training paired with 17 to 26% high-intensity training.
How to find your zone 2
Three ways to find it, from least to most equipment:
- Talk test. Run at a pace where you can speak in full sentences without gasping for air. Coaching site High North Performance describes zone 2 breathing as staying "conversational," and notes that Inigo San Millan recommends the talk test as a practical check when lab data isn't available.
- Heart rate percentage. Aim for 60 to 70% of your maximum heart rate, per the Garmin table above. Garmin's guide says the platform estimates your max heart rate initially with 220 minus your age, then refines that number from your activity data; treat the starting number as rough. Robert Robergs and Roberto Landwehr, in a 2002 paper in the Journal of Exercise Physiology Online, traced the 220-minus-age formula to a 1971 paper built by drawing a best-fit line through roughly 11 existing references, and reported the formula's error across the literature they reviewed at 7 to 11 beats per minute. A 2001 meta-analysis of 351 studies and 18,712 people by Hirofumi Tanaka, Kevin Monahan and Douglas Seals in the Journal of the American College of Cardiology found the formula overestimates max heart rate in younger adults and underestimates it in older adults, and proposed 208 minus 0.7 times age as a closer fit.
- Blood lactate. A lab test tracks how blood lactate concentration changes as effort rises. San Millan places zone 2 at roughly 1.5 to 2.0 mmol/L. This method is the most precise of the three, and the least accessible: it needs blood draws during a graded lab test.
These three methods don't always land on the same pace for the same person. A heart-rate-formula zone 2 is an age-based estimate; a lab-defined zone 2 is measured directly from that person's blood. Where they disagree, the lab number is the more precise one, and the formula number is the more convenient one.
Common mistakes in zone 2 running
- Running it too fast. Coach and author Matt Fitzgerald, who built the 80/20 training model, describes runners drifting into what he calls "Zone X", a gap between zone 2 and real threshold work that he says most runners land in without realizing it: an effort too hard to build the aerobic base zone 2 targets and too easy to count as real threshold work.
- Obsessing over the exact number. Heart rate can drift upward over a run even at a steady, unchanging effort. Coach Steve House, writing for Uphill Athlete, builds a standard aerobic-threshold test around exactly that: after a 10 to 15 minute warm-up, hold a fixed pace for 40 to 60 minutes, split the test into two halves, and compare average heart rate between them. House reads a gap of 3.5 to 5% as the test having found the runner's aerobic threshold, which is the heart rate the test started at. Under 3.5% means the starting heart rate was too easy, and House's instruction is to redo the test 5 bpm higher; over 5% means it started above the aerobic threshold, so redo it lower. Even in a test built to hold effort constant, the heart-rate number still moves by several percent, which cautions against treating a rising number mid-run as proof that effort rose too. Chasing a fixed number on the display can mean slowing down mid-run for a rise the effort didn't cause, or speeding up because the number reads low. The talk test, checked periodically, catches an effort change that a number alone can miss.
What to do with zone 2 once you have it
Finding your zone 2 is the setup; deciding how much of a training week lives there is the actual plan. The 80/20 running guide covers how that low-intensity, high-intensity split gets built into an actual week. Pace itself shifts with heat, terrain and fatigue even at a steady zone 2 effort, so checking average running pace over several weeks against that steady effort shows more than any single run's number. And because a fixed heart-rate number doesn't account for how much fatigue you're already carrying, Runked's training load, fitness and fatigue tracking adjusts for that day to day from your own training history.
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Download on App StoreFrequently asked questions
How do I find my zone 2?
The talk test is the simplest starting point: run at a pace where you can speak in full sentences without gasping for air. For a heart-rate number, Garmin's 5-zone model puts zone 2 at 60 to 70% of your maximum heart rate. If you don't have a tested max heart rate, 220 minus your age is one estimate, though a 2001 meta-analysis by Tanaka, Monahan and Seals in the Journal of the American College of Cardiology found age-based formulas like it can be off from a person's real max heart rate by a wide margin. A lab lactate test is more precise: physiologist Inigo San Millan places zone 2 at roughly 1.5 to 2.0 mmol/L of blood lactate, but it needs lab access a watch doesn't.
Is zone 2 the same as easy running?
They overlap but aren't identical. Zone 2 is one specific slice of effort, defined by a heart-rate percentage, a talk test, or a lab lactate number. Easy is a broader, informal word for anything that feels comfortable, and it's possible to feel like you're running easy while sitting above zone 2. Coach and author Matt Fitzgerald, who built the 80/20 training model, calls that in-between effort Zone X, a gap between zone 2 and real threshold work that he says most runners land in without realizing it.
How much of my running should be zone 2?
There's no single number that applies to everyone, but the evidence from elite endurance athletes leans heavily toward low intensity. A 2015 review by Stoggl and Sperlich in Frontiers in Physiology found elite Kenyan distance runners training at low intensity around 84% of the time, and top marathon runners around 78% before a race. A 2024 systematic review in the journal Sports, by Nost, Aune and van den Tillaar, included 14 training studies, 10 of which measured VO2max; 8 of those 10 showed improvement under a low-intensity-heavy plan, 5 of them statistically significant, with effect sizes the review describes as varying from trivial to large. From that evidence, the review's own recommendation was a distribution of roughly 75 to 85% low-intensity training paired with 17 to 26% high-intensity training. Those figures come from elite athletes' logs and training studies; they don't guarantee the same split works for any individual plan. Runked PRO's personalized training plans build a low-intensity-heavy week into your schedule automatically, based on your own training history.
Do I need a heart-rate monitor?
No. The talk test needs no equipment: if you can speak in full sentences without gasping, you're in the range zone 2 describes. A heart-rate monitor gives you a number to check that against, which helps most on days when heat, caffeine or nerves push your effort up before your legs feel it. Coach Steve House, writing for Uphill Athlete, uses a 40 to 60 minute test at a fixed pace, taken after a 10 to 15 minute warm-up and split into two halves, to find a runner's aerobic threshold. A heart-rate gap of 3.5 to 5% between those halves means the test found it; under 3.5% means the test started too easy and House says to redo it 5 bpm higher. Even an effort held perfectly constant moves the number by several percent, which is why a display number by itself can be misleading mid-run.