Guide
Amazfit Heart Rate Zones — The Right Way
Your Amazfit watch uses the 220-minus-age formula by default. That gives most runners wrong zones — too high for easy runs, too low for hard efforts. Here's how to find your real lactate threshold and set accurate zones.
Why default Amazfit zones are wrong
Out of the box, Amazfit calculates your heart rate zones using the formula: Max HR = 220 − age. It's simple, but the error is ±10–15 beats per minute. For a 35-year-old, the formula says max HR is 185 — but it could actually be anywhere from 170 to 200.
Wrong max HR means wrong zones. If your real max is 200 but Amazfit thinks it's 185, your Zone 2 boundary is set too low. Every easy run shows as Zone 3–4. You think you're pushing hard, but you're actually in aerobic range. Or worse — you slow down unnecessarily because the watch keeps beeping.
The fix: determine your lactate threshold heart rate (LTHR) and set zones based on that. LTHR is individual — no formula, no guessing.
How to find your lactate threshold
The lactate threshold is the intensity where lactate starts accumulating faster than your body can clear it. Your LTHR is the heart rate at this point. Here's a simple test anyone can do:
Warm up for 10 minutes
Easy jogging — don't rush. The goal is to get blood flowing and HR stable before the hard effort.
Run 30 minutes all-out
Start your Amazfit timer, then run as hard and evenly as you can for 30 minutes. This isn't a sprint — it's the hardest pace you can sustain. Think 10K race effort. Go too fast and you'll fade; too slow and the result won't be accurate.
Check the last 20 minutes
Open the workout in Zepp after you're done. Find the average heart rate for the last 20 minutes (not the full 30 — the first 10 minutes include HR ramp-up). That number is your LTHR.
T-Rex 3 Pro has a built-in LTHR test. Go to Workouts → Training → Lactate Threshold Test on the watch. Follow the guided protocol. The result shows your LTHR directly — no manual calculation needed.
Calculate your 5 zones
Use your LTHR to set zones based on Joe Friel's methodology. This is the most widely used system for endurance athletes:
Recovery
< 81%
Aerobic
81–90%
Tempo
90–94%
Threshold
94–100%
VO2max
> 100%
Example: LTHR = 170 bpm. Z1: below 138, Z2: 138–153, Z3: 153–160, Z4: 160–170, Z5: above 170. Use the STAS HR zone calculator for exact numbers based on your LTHR.
How to set zones in the Zepp app
Amazfit doesn't import zones from external sources. You need to enter them manually in the Zepp app:
Open zone settings
Zepp app → Profile (bottom right) → scroll to Workout settings section → Heart Rate Zones. You'll see the current zones based on the 220-age formula.
Switch to custom zones
Tap to edit. Enter the lower and upper boundary for each zone based on your LTHR calculation. Save.
Verify on the watch
Start a workout on your Amazfit. Check the zone display — it should now show your custom zones. During easy runs, you should be solidly in Zone 1–2.
Limitation: Amazfit uses ONE set of zones for all sports. If you run and cycle, your cycling zones should ideally be 5–10 bpm lower — but Zepp doesn't support sport-specific zones. Intervals.icu does.
HR zones by Amazfit model
All current Amazfit models support custom heart rate zones through the Zepp app. Here's what each model adds:
Built-in LTHR test, optical HR, 25-day battery. The most feature-complete Amazfit for runners. Also supports workout push from Intervals.icu.
Optical HR, custom zones via Zepp. Workout push from Intervals.icu supported. Good all-around smartwatch for runners.
AMOLED display, 25-day battery. Accurate optical HR. No built-in LTHR test — use the manual 30-minute method.
Dual-band GPS for runners. Zepp Coach integration. Custom zones via Zepp. Best GPS accuracy in the Amazfit lineup.
Automatic zones from training data
Manual zone setup works, but zones shift as your fitness changes. Intervals.icu recalculates your zones automatically based on workout data — specifically, it uses your heart rate distribution across training sessions to detect threshold shifts.
Connect your Amazfit to Intervals.icu, and your zones stay current without repeated testing. STAS passes these zones to ChatGPT, so your AI coach always works with accurate data.
Frequently asked questions
Why is the 220 minus age formula inaccurate?
It's a statistical average with ±10–15 bpm error. Two runners of the same age can have max HRs differing by 25+ beats. A lactate threshold test gives individual results — no formulas, no guessing.
Does Amazfit support a built-in lactate threshold test?
T-Rex 3 Pro has a guided LTHR test under Workouts → Training. On other models (Balance 2, Active Max, Cheetah Pro), run a 30-minute all-out effort and check the average HR for the last 20 minutes in Zepp.
Are heart rate zones the same for running and cycling?
No. Cycling HR is typically 5–10 bpm lower than running at the same effort. Amazfit uses one set of zones for all sports — this is a known limitation. Intervals.icu supports separate zones per sport.
How often should I recalculate zones?
Every 2–3 months, or after a significant fitness improvement. If you're running faster at the same heart rate — your threshold has shifted upward and zones need updating.
Can I set zones automatically on Amazfit?
Not in Zepp — manual entry only. However, Intervals.icu calculates zones automatically from your training data. The zones on your watch are just for the in-workout display; your actual training analysis happens in Intervals.icu.
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