Is zone 2 overrated? What the evidence says about easy cardio and weekly minutes

In physiology, zone 2 is exercise just below the first lactate or ventilatory threshold: the point where lactate in the blood starts to rise above its resting level. It is a property of your body, found in a lab, not a fixed heart rate.

In practice it is usually set as a percentage of maximum heart rate. A lab study of 100 people shows why that is rough: their lactate threshold fell anywhere from 60% to 90% of maximum heart rate, and from 45% to 74% of VO₂max. The authors say fixed percentages "conform poorly" to the intensity domains. A review by Jamnick and colleagues found that a fixed percentage "has little merit" for producing the responses of a given domain.

So a band of, say, 65–75% of maximum can sit below one person’s threshold and above another’s. These are lab studies. They show a heart-rate band is a rough proxy, not that it is useless.

The band is a percentage of a predicted maximum, which adds a second estimate. The best-supported formula is 208 − 0.7 × age, from a meta-analysis of 18,712 people, with no difference between men and women. It reads higher than 220 − age in older adults: at 70 it gives 159, against 150.

It is a population average. Your own maximum can sit well above or below it, and every zone built on it moves with it.

Storoschuk and colleagues reviewed the case for zone 2 in 2025. They concluded that the evidence does not support it as the best intensity for mitochondrial or fat-oxidation gains in the general public, and that higher intensities matter more when total training time is low. They note that much of the case for zone 2 rests on observational data from elite endurance athletes who train at high volume.

It is a narrative review rather than a meta-analysis, and one author declares equity in an exercise-related company.

Overrated is not useless. A meta-analysis of 28 trials in 723 healthy adults aged 18–45 found that steady endurance training raised VO₂max by 4.9 mL/kg/min against no exercise, and interval training by 5.5. Intervals came out ahead by 1.2. Both moved it a lot. The trials were short and in young adults.

The WHO 2020 guideline asks adults for 150–300 minutes of moderate or 75–150 minutes of vigorous aerobic activity a week, or a mix, plus muscle strengthening. It counts all moderate-to-vigorous activity, not zone 2.

The mortality data follow that shape. In 661,137 people across six pooled cohorts, hazard ratios against no activity were 0.80 below the minimum, 0.69 at one to two times it, 0.63 at two to three times, 0.61 at three to five times and 0.69 at ten times or more. Most of the gain came early. In a second study of 116,221 people over 30 years, meeting the moderate guideline went with 19–25% lower mortality, and 300–599 minutes with a further 3–13%. The near-maximal association came at 300–600 minutes of moderate or 150–300 minutes of vigorous activity a week.

Intensity is not the whole story either. Measured by accelerometer in 36,383 adults with a mean age of 62.6, the most active quarter had about a quarter of the risk of the least active (0.27), and light activity alone showed a similar gradient (0.38 for the top quarter). Short follow-up makes reverse causation likely: people who are ill move less. For daily steps, risk levelled off at about 6,000–8,000 a day for people 60 and over and 8,000–10,000 under 60.

All of this is observational. No study in our sources shows that zone 2, as opposed to total activity or harder work, lowers mortality.

Longstanding estimates zone 2 from your workouts. A workout counts when its average heart rate falls within 65–75% of your Tanaka maximum, and the app shows your weekly minutes as a share of 150, never as a percentile. For many people that band is not their physiological zone 2, so read the number as moderate-intensity minutes. For a 50-year-old, Tanaka gives a maximum of 173, which puts the band at about 112–130 beats a minute.

The rule has edges. A whole workout counts if its average lands in the band, so an interval session can count in full, and a steady session averaging just above the band counts not at all. Vigorous minutes, which count double in the WHO guideline, are not added, so the share can understate what you do.

The app does not tell you zone 2 is the best way to train. When VO₂max is behind your line, its cue is one interval session a week (4 × 4 minutes hard) on top of steady work; the trials say either kind of work moves it. Details are on the zone 2 test page. This is not medical advice.