What is Zone 2 heart rate?

What does Zone 2 mean?

Zone 2 is easy running you can keep up for a long time. Your breathing is deeper than at rest and stays even. You can still talk in full sentences.

A 2025 panel of 14 sport scientists and coaches agreed that Zone 2 training is best done right below the first lactate or breathing threshold.^[1] A session can be one steady run, a run with changes of pace or a set of intervals.

Labs find that threshold in two ways. LT1 is the first lactate threshold. It is the point where lactate in your blood first starts to rise above its resting level. VT1 is the first breathing threshold. It is the point where your breathing starts to climb faster than the work. Both mark the top of easy effort.

Diastra calls this band Easy. Easy is the Zone 2 you know, and its top edge is drawn where blood tests on runners find LT1. Type your age below to see yours.

Why does Zone 2 mean different things on different charts?

Lab tests find two lines in your effort. Below the first line, lactate in your blood stays near its resting level. Above the second line, lactate climbs steeply.

Scientists used those two lines to split training into three zones. A 2006 study of 11 young cross-country skiers drew its zones from the two breathing thresholds.^[2] Zone 1 was everything below the first threshold. Zone 2 was the space between the two thresholds. Zone 3 was everything above the second one. About 75% of the skiers' endurance sessions stayed in zone 1, and only about 8% fell in zone 2.

A 2007 study of runners used the same three zones.^[3] In those studies, zone 2 meant the moderate middle.

Coaches also use scales with more zones. A scale used for world-class distance runners has seven.^[4] Its zone 1 runs from 60 to 72% of max, and its zone 2 runs from 73 to 82%. Both zones are low intensity on that scale.

Studies of top athletes found that most of their training is easy. World-class distance runners do at least 80% of their running at low intensity all year round.^[4] A 2010 review of top endurance athletes found about 80% of their sessions at low intensity.^[5] About 20% were built around hard work such as intervals. Training that is mostly easy with a little very hard work is often called polarized training or 80/20 running.

Today Zone 2 gets a lot of attention, and many people say a large share of training should happen there.^[1] The same 2025 panel noted that coaches, athletes and scientists had no clear agreement on what Zone 2 means.

So the name now points at three different bands. One is the 60 to 70% band on popular charts. Another is zone 2 of the world-class scale, which runs from 73 to 82%. The third is the three-zone model's middle zone, which runs between the two thresholds.

Why does the 60 to 70% chart stop early?

Many charts put Zone 2 at 60 to 70% of max.

Blood tests put the first threshold higher for most runners. Nuuttila and colleagues tested 165 runners on a treadmill.^[6] They were 20 to 50 years old, and all of them ran regularly. The men reached LT1 at 78.9% of max on average. The women reached it at 83.6%.

Run the numbers for a max of 180. The 70% line is 126 beats a minute. The average man in that study would reach LT1 near 142 beats. The average woman would reach it near 150. A 70% cap leaves that whole stretch of easy running outside Zone 2 for the average runner.

Runners and their coaches draw the line higher too. A 2025 survey asked endurance coaches and athletes where each zone on their five-zone scale starts.^[7] Runners started zone 2 at 69.8% of max on average and zone 3 at 79.6%. So the zone 2 that runners use runs up to about 80% of max.

The world-class scale shows the same gap. Its 60 to 72% zone is listed for warm-ups, cool-downs and easy long runs.^[4] Its next zone up runs from 73 to 82%, and the paper lists it for long runs, uphill runs and progressive runs.

Some runners say Zone 2 feels absurdly slow. The 70% line is one reason. Why Zone 2 running feels so slow covers it in detail.

What is the research edge for Zone 2?

The top of Zone 2 in the research is LT1. Blood tests on the 165 runners in the 2025 lactate study put it at 80.7% of max on average.^[6] Two things change where it lands.

Women reach it at a higher share of max

The lactate study found LT1 at 83.6% of max for women and 78.9% for men. Its authors wrote that this points to “a need for sex-specific intensity anchors.”^[6] A breathing study of more than 1,200 people found the women's average higher than the men's at every training level.^[8]

People with more training reach it at a higher share

The breathing study grouped people by how trained they were.^[8] Men went from 74.6% of max in the least trained group to 80.8% in the most trained. Women went from 77.9% to 82.9%.

Diastra's Easy band follows the lactate numbers. Easy runs from 60% of max up to 79% for men and 83% for women, and up to 80% when sex is not given. Diastra rounds the women's 83.6% down to 83%. The Zone 2 heart rate calculator turns those edges into beats a minute.

How far can your own Zone 2 be from the average?

Averages hide a wide spread. Nuuttila's team gave each runner the average LT1 percentage for their sex. They applied it to the max each runner reached on the treadmill.^[6] The real LT1 fell within about 16 beats above or below that estimate for 95 of every 100 runners. Heart rate reserve did no better. That method uses your resting heart rate as well as your max.

Sixteen beats is a wide miss. It is about 9% of a 180 max.

The study also checked a fixed line at 80% of max. At that line, 57 of every 100 runners were still below their own LT1, and 43 were already above it.^[6] So a fixed percentage can show Zone 2 when you are already past your own first threshold.

Feel stays useful for that reason. Slow down when you cannot talk in full sentences, even if your watch still shows Zone 2. A sports lab test with blood samples or a breathing mask finds your own line.

What does Zone 2 feel like?

Zone 2 feels easy and steady. You breathe deeper than at rest, and the rhythm stays even. You could hold a conversation the whole way.

Researchers also rate effort on a numbered scale that runs from 6 to 20. Higher numbers mean harder effort. The runners in the lactate study rated LT1 at 12.5 on average.^[6] A study of 863 exercise tests found the same 12.5 at the first breathing threshold whatever the person's fitness.^[9]

The world-class scale lists effort on the same 6 to 20 numbers.^[4] It rates its lowest zone at 9 to 12 and its long-run zone at 12 to 14. It rates its hardest intervals at 18 to 20.

How much of a week goes to Zone 2 in the research?

Most of it. World-class distance runners do at least 80% of their running at low intensity all year round.^[4] Low intensity on their scale covers both zone 1 and zone 2.

Trials that change the mix point the same way. The 2007 study split 12 trained runners into two groups for five months.^[3] One group did 80.5% of its training below the first breathing threshold. The other did 66.8% there and more of its training between the thresholds. The share of very hard work was about the same in both groups. Both groups ran a 10.4 km race faster. The mostly easy group improved by 157 seconds, and the other group by 121.5 seconds.

A 2014 study split 48 well-trained endurance athletes into four groups for nine weeks.^[10] The polarized group did mostly easy work plus very hard intervals. It raised VO₂peak by 11.7%. VO₂peak is the most oxygen the body used in the test. The group that trained mostly at threshold did not raise its VO₂peak. Neither did the group that trained mostly long and easy.

Hours matter when you read this study. The polarized group trained 104 hours, and the threshold group trained 84. The mostly long-and-easy group trained 102 hours, which is about the same as the polarized group. Every athlete had already trained mostly long and easy before the study. So the long-and-easy group kept training much the way it already did.

The 80/20 split is a rule of thumb. The polarized group in that study did 68% of its sessions easy, 6% at threshold and 26% hard.^[10] The 2025 panel also expected that Zone 2's gains could come from runs a little harder or easier.^[1]

Diastra calls the space between Easy and Threshold the gray band. The group with more time between the thresholds in the 2007 study still got faster. Its gain was smaller than the mostly easy group's gain.

How do you find your own Zone 2?

1. Find your max. Every percentage needs a max. Tanaka's formula gives a first guess of 208 minus 0.7 times your age.^[11] One person's real max can be far from any formula. A study of 3,320 healthy adults built its own age formula from all-out tests.^[12] Real maxes in that study often landed 11 or more beats above or below its formula. A max from a hard race or a guided test comes closer. The max heart rate calculator compares the formulas.
2. Draw your band. Diastra's Easy band runs from 60% of your max to 79% for men and 83% for women. The calculator above does the math in beats a minute.
3. Check it against feel. If you cannot talk in full sentences, slow down.
4. Test in a sports lab for your own line. A sports lab finds your own LT1 with blood samples or a breathing mask.

To set these edges on your wrist, see heart rate zones on Apple Watch.

How does Diastra draw Zone 2?

Diastra draws this band from your own Apple Watch workouts. It reads every workout your watch saved in Apple Health. It finds your max heart rate from your hardest efforts, a guided test or a number you type, and it tells you which one it used. Your Easy band runs from 60% of that max to 79% for men and 83% for women. The watch taps your wrist when you drift out of Easy on a run. Only the minutes that held get credit, and Diastra shows over the weeks whether your training is working.