Zone 2, explained without the hype

Think of it as the top of easy. Peter Attia is a physician and the author of the longevity book Outlive.³ He describes Zone 2 as the highest effort at which your body clears lactate as fast as it makes it.

The name comes from training systems that split effort into five or more zones, and coaches don't all draw the lines in the same place. A 2025 panel of 14 sport scientists and coaches agreed that Zone 2 sits just below the first lactate or breathing threshold.⁴

In plain terms, Attia says, it's a speed slow enough to keep up a conversation.³ It's also fast enough that the conversation feels a little strained.

Bottom line

Zone 2 is the fastest pace that still feels steady, just below where your breathing changes.

The simplest gauge of Zone 2 is your voice. If you can speak in full sentences but would rather not, you're about right.

That's called the talk test. A 2014 review found that comfortable speech is usually possible below the breathing and lactate thresholds and usually isn't above them.⁵ The test gave consistent results for walking, jogging, cycling and other machines, and it costs nothing.

Heart rate gives a rougher guide. Attia puts Zone 2 at roughly 70 to 85 percent of your true maximum heart rate, depending on fitness.³ In a 2011 lab study of 15 young adults, people could still talk comfortably up to about 82 percent of their maximum heart rate.⁶

For someone whose maximum heart rate is 180, 70 to 85 percent works out to about 126 to 153 beats a minute. Attia notes that for some people, a brisk walk or an uphill walk already reaches Zone 2.³

Bottom line

If you can talk in full sentences but would rather not, you're in Zone 2. Your watch is a backup, not the judge.

Regular endurance training changes how your heart is controlled. Your resting heart rate drops, and so does your heart rate at any easy pace.

A 2003 review explained the main reason.¹ Endurance training turns up the calming branch of your nervous system and turns down the branch that speeds the heart up.

Fitness rises too. A 2015 review pooled 28 studies with 723 healthy adults.² Steady endurance training raised peak oxygen uptake, the standard lab measure of aerobic fitness, by about 4.9 mL/kg/min compared with doing nothing.

That fitness matters for your lifespan. A 2018 study followed 122,007 patients who took a treadmill test.⁷ Those in the lowest fitness group were about five times as likely to die during follow-up as the fittest group. Low fitness carried a risk as large as smoking or diabetes, or larger.

Bottom line

Easy running slows your resting heart and raises your fitness, and higher fitness goes with a longer life.

Easy work helps, but one popular claim goes past the evidence. That claim says Zone 2 is uniquely good for your mitochondria, the parts of your cells that turn fuel into energy.

Much of the enthusiasm comes from studies of elite athletes, who do huge amounts of easy work. A 2018 study found that professional endurance athletes burned more fat and made less lactate at the same effort than less fit people.⁸ A 2010 review of top endurance athletes found that about 80 percent of their sessions were at low intensity.⁹

Those athletes train 10 to 13 times a week, though, and you probably don't. A 2025 review argued that the evidence doesn't make Zone 2 the best intensity for improving mitochondria.¹⁰ It concluded that harder exercise matters more when training time is short.

The 2015 review points the same way. Hard intervals raised fitness by about 5.5 mL/kg/min against 4.9 for steady work, a small gap that favored the harder sessions.² Even the 2025 expert panel expected Zone 2's benefits to show up at slightly harder and easier efforts too.⁴

Bottom line

Zone 2 is a good base. If you only have two or three hours a week, some of them should be harder.

If you're new to it, start with two 30-minute sessions a week and build toward about three hours.³

Attia writes that even two 30-minute sessions a week help beginners.³ For steady gains, he puts the minimum for most people at about three hours a week, or four 45-minute sessions. He bases that on talks with exercise scientists, not on a trial.

Your Zone 2 pace will get faster as you get fitter, so the same effort will carry you farther over the months. That's the change to track, not the heart rate number on any single day.³

Bottom line

Two 30-minute sessions a week is a good start, and about three hours a week is a solid target.

1. 01

   Zone 2 is the hardest steady pace you can hold while still speaking in full sentences.

2. 02

   For many people that means roughly 70 to 85 percent of maximum heart rate, and for beginners it may include walking.

3. 03

   Steady endurance training lowers your resting heart rate and raises aerobic fitness.

4. 04

   Hard intervals raise fitness about as much or a little more, so Zone 2 isn't the only route.

5. 05

   Start with two 30-minute sessions a week and build toward about three hours.