The cardio guide

What is zone 2 training, in plain words?

By GyroscopeUpdated November 15, 20267 sources

Zone 2 is an easy, steady pace where you’re breathing a little deeper but can still talk in full sentences. Watches set it at 60 to 70% of your max heart rate. It’s a fine pace for most of your cardio, and the evidence says the hard minutes on top still matter, above all when your week is short.

A few years ago almost nobody outside endurance sports had heard of zone 2. Now it’s on every longevity podcast, and the pitch goes something like this: slow, long sessions train your mitochondria to burn fat, elite cyclists do hours of it, so that’s how the rest of us should train too. People who used to walk briskly started slowing down on purpose and worrying that their heart rate drifted too high on a hill.

Part of that is right. Easy, steady cardio is good for you, it’s pleasant, and you can do a lot of it without getting hurt or worn out. The part that doesn’t hold up is that it’s the best kind, or that harder efforts somehow undo it.

What are the five zones?

Heart rate zones split effort into five bands by your max heart rate, the fastest your heart can beat. Gyroscope’s old Cardio Guide used the same five that most watches use today. Each zone also has a feel, which is the part you can use without a watch.

The max heart rate in that table comes from a formula, 208 minus 0.7 times your age, which predicts the average person well and any one person less well. At 50 it gives 173, so zone 2 lands at 104 to 121 beats a minute. Your real max may be higher or lower, and then the whole zone slides with it. That’s why the talk test is a better guide than the beats. vo2max.guide’s heart rate zones calculator compares three formulas and takes a measured max if you have one.

Why did zone 2 get so famous?

Because elite endurance athletes do a lot of it. They train huge volumes, much of it easy, and they have big aerobic engines and muscles packed with mitochondria. It’s a short jump from there to “easy training builds the engine”.

In 2025, four exercise scientists looked at that jump in a review called “Much Ado About Zone 2”. They found the popular advice “largely” came from watching elite athletes who train huge volumes. Their conclusion was that current evidence doesn’t support zone 2 as the best intensity for improving mitochondria or fat-burning capacity, and that harder efforts above zone 2 are “critical” for heart and metabolic health, “particularly in the context of lower training volumes.”

An athlete with 20 hours a week to train can afford to keep most of it easy. Someone with three hours a week gets more from making some of it hard.

What does the evidence say about easy versus hard?

Steady training works well. In 28 trials of healthy adults, steady cardio of all kinds raised VO2 max by about 4.9 ml/kg/min against no exercise. Intervals raised it by about 5.5, a small edge. In the 4x4 trial, moderately trained men who ran 4 rounds of 4 hard minutes raised their VO2 max more than men who did the same total work slow and steady at about 70% of max heart rate.

For a long life, the pattern is similar. In 116,221 US health professionals followed for 30 years, hard minutes went with extra benefit in people doing under 300 brisk minutes a week. Above that, the steady minutes seemed to cover it.

A picture from daily life

Think of saving money. Putting a little aside every week, steadily, builds most of your savings, and it’s hard to mess up. A raise speeds things up a lot. If you have years and a big steady income, you’ll get there on saving alone. If you’re short on time, the raise is what makes the difference. Zone 2 is the steady saving. Hard minutes are the raise.

Do it once: find your zone 2 on a walk

You don’t need a lab or even a watch. Try this on your next walk, ride or jog:

1. Warm up for five minutes at an easy pace.
2. Speed up until you notice your breathing. Say a full sentence out loud, like your address. If it comes out easily, speed up a little more.
3. Find the edge. Zone 2 is the fastest pace where you can still say a full sentence without gasping. If you can only get out a few words, you’ve gone into the hard zones.
4. Hold it for 20 minutes and note how it feels, and your heart rate if you wear a watch. That’s your zone 2, for your body, today.

As you get fitter, the same pace usually feels easier, and you’ll need to go a little faster to find the edge again. That’s the sign it’s working.

Is zone 2 the fat-burning zone?

Your body does burn a larger share of fat at easy paces, which is where the idea comes from. But burning fat during a workout isn’t the same as losing it from your body, which comes down to your whole day. bodyfat.guide covers it in the fat-burning zone myth.

So should I bother with zone 2?

What we still don’t know

Most of the trials comparing easy and hard training were short and in young adults, and very few measured zone 2 the way watches define it. Nobody has followed people assigned to zone 2 against harder training for decades. The full argument about zone 2 and VO2 max is on vo2max.guide: is zone 2 the best way to raise VO2 max? and what heart rate is zone 2?