Emma Richardson
Why Heart Rate Zones Are Worth the Faff
A stopwatch and a GPS watch tell you what you did. Heart rate tells you what it cost you. For runners and cyclists, that distinction matters more than most people realise. Two athletes can run the same pace on the same morning, and one is cruising in a comfortable aerobic rhythm while the other is grinding well above threshold, digging a hole they will pay for on Thursday. Heart rate zones give you an honest picture of internal effort, which is the number your body actually responds to.
At their simplest, zones split your usable heart rate range into bands, each nudging a different energy system. Train in the right bands often enough and you build a bigger aerobic engine, sharper top-end speed and a body that recovers between sessions. Train everything at the same medium-hard effort and you get the worst of both worlds: too hard to recover from, too easy to sharpen you.
The Five Zones, and What They Feel Like
Most coaching models use five bands, based on a percentage of maximum heart rate or, more usefully, a percentage of your lactate threshold heart rate. Here is how they translate into real life on the road or trail.
- Zone 1 — recovery (roughly 50–60% of max): a gentle spin or shuffle. You could hold a full conversation and sing badly if asked. Use it after hard days, and for warm-ups and cool-downs.
- Zone 2 — aerobic base (60–70%): comfortable, sustainable, slightly boring. Talking in full sentences is easy and you could keep going for hours. This is where most endurance fitness is built.
- Zone 3 — tempo (70–80%): the "comfortably hard" band. Conversation shortens to a sentence or two. Useful in small doses, but it is the zone most people live in by accident.
- Zone 4 — threshold (80–90%): hard but controlled. You could hold it for 20–40 minutes in a race, but only just. Short bursts of speech only. Excellent for sharpening race pace.
- Zone 5 — VO2 max and above (90–100%): very hard, breathing ragged, intervals measured in minutes rather than hours. Powerful, but you can only manage a limited dose each week.
If you want a rough ceiling before testing properly, the old 220-minus-age formula is a starting point and nothing more — it can be wrong by ten to fifteen beats either way. The talk test and your own rating of perceived effort are surprisingly accurate cross-checks.
Finding Your Own Numbers
Generic zones from an app are better than nothing, but you deserve better than nothing. A simple field test will do the job.
- Threshold test (runner): warm up thoroughly, then run a hard but even 30-minute effort. Your average heart rate over the final 20 minutes is a good estimate of your lactate threshold heart rate. Set Zone 4 to sit just below it and build the other bands around it.
- Threshold test (cyclist): the same idea, but on a trainer or a steady climb for 20 minutes, taking the average of the last 15. Pacing matters — start too hard and the number is useless.
- Resting heart rate: measure it on waking, before you move. Tracking it over weeks is one of the simplest ways to spot accumulating fatigue or illness.
- Retest every six to eight weeks: as fitness improves, the same pace produces a lower heart rate, so your zones shift. Numbers from last spring are a history lesson, not a plan.
Building a Week Around the Zones
The most reliable pattern for endurance athletes is roughly 80% of training time in Zones 1 and 2, with the remaining 20% split between Zones 4 and 5. It feels counter-intuitive — the easy sessions feel far too easy, and the hard ones are genuinely grim — but it works.
A practical week for an active adult might look like this:
- Two easy Zone 2 sessions of 45–90 minutes
- One threshold session: 3 x 8 minutes in Zone 4 with 3 minutes easy between
- One short interval session: 6 x 2 minutes in Zone 5 with equal recovery
- One recovery session in Zone 1, or a full rest day
- One longer ride or run, mostly Zone 2, with the last 10 minutes in Zone 3 if you feel good
If you are a personal trainer working with general clients rather than competitors, the same logic applies in smaller doses — a couple of steady Zone 2 blocks on the bike or treadmill, one short set of harder efforts, and honest recovery in between.
What Heart Rate Cannot Tell You
Heart rate is a superb tool with real limitations, and knowing them stops you over-reacting to the wrong number.
- Cardiac drift: heart rate creeps upwards during long sessions even at a constant pace, especially in the heat. Do not panic and slow to a crawl — check how you actually feel.
- Lag: heart rate takes 30–90 seconds to catch up with effort. Judge short intervals by pace, power or feel, and read the averages afterwards.
- Daily noise: caffeine, poor sleep, stress, dehydration and altitude all push heart rate up. A high reading on a tired day is information, not failure.
- Hills and heat: both raise heart rate for the same effort. Let the numbers flex rather than chasing a fixed ceiling up a climb in August.
Making Zones Stick
Use heart rate alongside pace, power and how you feel, never instead of them. Review your sessions weekly: were the easy ones truly easy, and the hard ones truly hard? If every run sits in Zone 3, that is the first thing to fix. Keep a simple note of how sessions felt next to the numbers, and patterns will appear within a month. Zones are not a rulebook — they are a way of being deliberate about the work you are asking your body to do.
