Heart Rate Zone Training: How to Set Your Zones and Use Them

Heart rate zones turn "go easy" and "push hard" into numbers. Instead of guessing, you hold a heart rate range that matches what the session is for, whether that's an hour of easy base building or four minutes at the edge of your capacity. Every running watch and most cardio machines now show zones, but the default settings are often wrong for you, and wrong zones make the whole idea useless.

Here's how to set them properly, what zone 2 and zone 3 training are actually for, and how to split your week between them.

Step 1: find your maximum heart rate

Every zone is a percentage of your maximum heart rate, so this number matters more than anything else. There are three ways to get it, from least to most accurate.

Use a better formula. The familiar 220 minus age is off by a wide margin for many people. A large meta-analysis of 351 studies and over 18,000 people, followed by a lab validation in 514 adults, produced a more accurate equation: 208 minus 0.7 times age (Tanaka, Monahan and Seals, 2001). For a 50 year old that gives 173, against 170 from the old formula. The gap grows with age.

Do a field test. After a proper warm-up, run or row hard uphill for three minutes, recover for two, then go again flat out for two to three minutes. The highest number your chest strap records is close to your real max. Only do this if you're healthy and already training regularly.

Get tested. A lab or clinic ramp test gives a true max and often your lactate threshold too. It's the gold standard, and overkill for most people.

Step 2: set your five zones

Most watches and apps use a five-zone model based on percentage of max heart rate. The boundaries vary slightly between brands, but this is the common version:

Zone	% of max HR	How it feels	What it trains
1	50 to 60%	Very easy, a brisk walk	Recovery, warm-ups
2	60 to 70%	Easy, full sentences	Aerobic base, fat use, endurance
3	70 to 80%	Moderate, short sentences	Aerobic fitness, tempo
4	80 to 90%	Hard, a few words	Lactate threshold
5	90 to 100%	Flat out, no talking	VO2 max, top-end speed

For that 50 year old with a max of 173, zone 2 runs from 104 to 121 bpm and zone 4 from 138 to 156 bpm.

If you know your resting heart rate, the Karvonen method (percentage of heart rate reserve, meaning max minus resting) personalises zones further. Garmin, COROS and Amazfit all offer it in their settings as "HRR".

Step 3: split your week sensibly

The best-supported pattern for endurance is simple: most sessions easy, a few genuinely hard, and not much in between. Coaches call it polarised or 80/20 training.

The evidence for it is real but smaller than the internet suggests. A 2024 meta-analysis of 17 studies found polarised training improved VO2 max a little more than other intensity splits, but only in programmes under 12 weeks and mainly in highly trained athletes; time trial performance came out the same either way (meta-analysis of polarised training). So the split isn't magic. Its big advantage for ordinary people is that it stops every session drifting into zone 3, which is hard enough to tire you out and too easy to push your top end.

A realistic week for someone doing four cardio sessions looks like this:

1. Two or three zone 2 sessions of 40 to 60 minutes. Run, row, cycle or use a cross trainer.
2. One interval session. For example, five rounds of four minutes in zone 4 with three minutes easy between. Rowing machine HIIT works well here.
3. Nothing hard the day after the interval session.

For general health rather than race fitness, the NHS asks for 150 minutes of moderate activity or 75 minutes of vigorous activity a week (NHS physical activity guidelines). Zone 2 and 3 count as moderate; zones 4 and 5 count as vigorous.

Zone 3 training: useful, but easy to overdo

Zone 3 sits at 70 to 80 percent of max heart rate, which for our 50 year old with a max of 173 is roughly 121 to 138 bpm. You can still talk in short sentences but you wouldn't choose to, and for a lot of recreational runners it's close to marathon pace.

That's the case for it. If you're training for a half or full marathon you need some time at race effort, and a tempo run in upper zone 3 teaches you what that pace feels like on tired legs. Longer steady efforts on a rower or bike at a strong clip live here too, and as one session in a week there's nothing wrong with that.

The trouble is that zone 3 is where unplanned training ends up. An easy run that creeps up because you feel good, or a spin class that never quite gets hard, both land there; do enough of them and you're too tired for proper intervals without having gone easy enough to recover. That's the drift the 80/20 split above exists to stop. Plan zone 3 sessions on purpose, keep them to about one a week unless you're in a race-specific block, and if an easy day starts drifting up into it, slow down.

Common mistakes

• Trusting the default max. Watches start with an age formula. Update it once you've seen a higher number in a hard effort, or your zones will sit too low forever.
• Running zone 2 too fast. Real zone 2 feels embarrassingly slow at first, and many runners have to walk up hills to stay in it. That's normal, and your pace at the same heart rate improves over weeks.
• Chasing zones in intervals. Heart rate lags effort by 30 to 60 seconds, so a 30 second sprint never shows zone 5. Use pace, power or perceived effort for short reps and let heart rate confirm afterwards.
• Relying on the wrist for hard sessions. A 2025 study against a Polar H10 chest strap found wearables were accurate at rest and on steady treadmill work but badly off during burpees (study on wearable heart rate accuracy). For intervals and circuits, wear a strap.
• Ignoring the day. Poor sleep, heat, caffeine and illness all raise heart rate. If zone 2 pace suddenly feels hard, the sensible move is an easier day.

What kit you need

A chest strap is the single best upgrade for zone training; our heart rate monitor guide ranks the options, most of which pair with any watch or gym machine. For the watch itself, the Amazfit Balance 3 and Garmin Forerunner 265 both handle custom zones, heart rate reserve and strap pairing without fuss, and the Amazfit Cheetah 2 Ultra is the one for long trail days.

Recommended reads

1. The best heart rate monitor in the UK
2. Amazfit Cheetah 2 Ultra review
3. Rowing machine HIIT workout
4. The best Garmin watch in the UK