Heart-rate zones are bands of effort, each tied to a training purpose. In the common five-zone model, zone 1 is recovery-easy, zone 2 is the conversational aerobic pace you could hold for a long time, zone 3 is comfortably-hard tempo work, zone 4 sits around the threshold where sustainable turns unsustainable, and zone 5 is the near-maximal territory that intervals visit briefly. The purposes are solid; the boundary numbers are estimates. Treat the zone chart as a map sketched in pencil, not a survey measured to the centimetre.
The five zones, translated
| Zone | Feels like | Main job |
|---|---|---|
| 1 | Barely exercise — you could do it all day | Warm-ups, cooldowns, recovery movement |
| 2 | Easy rhythm; full sentences possible | Building the aerobic base that supports everything else |
| 3 | Working; short sentences only | Sustained tempo efforts — and the zone easiest to overuse |
| 4 | Hard; a few words at a time | Threshold work that teaches a hard pace to be repeatable |
| 5 | Very hard; conversation is off the menu | Short near-maximal intervals that push your ceiling |
Different systems slice the percentage boundaries differently — which is itself a clue. The exact cut-lines matter far less than recognizing which of these five efforts a given session is asking from you.
Why 220-minus-age is a rough sketch
Most default zone settings estimate your maximum heart rate from a formula, and formulas miss real individuals by a wide margin. Plenty of people have true maximums well above or below their age-predicted number, with no health meaning either way — it's individual wiring, not fitness. Get the max wrong and every zone shifts with it: the 'zone 2' on your watch might genuinely be your zone 3, which quietly ruins easy days.
You don't need a lab to fix this. Over weeks of training, the highest readings you see at the end of your hardest efforts sketch a working ceiling, and cross-checking zones against the feels-like column above catches most mislabels. When feel and formula disagree, trust the pattern of observations.
Zones as an interval pacing tool
In interval training, zones give shape to both halves of the work-rest cycle: efforts should climb into the top bands by their final seconds — heart rate trails effort, so don't expect it to arrive instantly — and recoveries should fall far enough that the next round can be honest. Live in-class displays make that rise-and-fall visible while you train; heart-rate training is built around exactly that loop, and the broader case for training with data is made in why train with a heart-rate monitor.
As for how much of your week belongs in each band — most of it low, a deliberate sliver high — that intensity-distribution question is answered in HIIT versus LISS.
Common questions
Why can't I ever reach zone 5?
Often because your zones are anchored to a formula-estimated max that's lower than your real one, so 'zone 5' starts at heights the chart placed wrong. It also simply takes a fresh day and a long enough effort — heart rate climbs reluctantly.
Why does my heart rate peak after the interval ends?
Lag. Heart rate needs time to reflect effort, so a short hard burst frequently tops out during the recovery that follows it. It's normal — and it's why very short intervals are better paced by feel or output than by chasing the live number.
Are the default zones on my watch accurate?
Out of the box they're formula-based guesses — a reasonable starting point, nothing more. If you routinely see readings above your supposed maximum, raise the max in the settings; a real observation beats a default every time.
Are my zones the same for every kind of exercise?
Not exactly. Most people run a little lower on a bike than on a treadmill at an equivalent effort, and different again in the pool. If you train across modes, let feel calibrate the numbers instead of forcing one chart onto everything.
