Why Your LTHR Zone 2 Is Higher Than Your %HRmax Zone 2

If you switched your watch to LTHR-based zones and your Zone 2 jumped 20–30 beats, nothing is broken. "Zone 2" is a label, and different zone systems pin it to different intensities. A Garmin-subreddit PSA about this went viral for a reason.

The short answer

The two systems use different reference points and different percentages:

• %HRmax zones anchor to your maximum heart rate. In the standard 5-zone version, Zone 2 is 60–70% of HRmax.
• LTHR zones (Joe Friel's model) anchor to your lactate-threshold heart rate, which sits near the top of your range. In the running version, Zone 2 is 85–89% of LTHR.

A high percentage of a high anchor lands higher than 60–70% of max. Same name, different intensity. Compare the %HRmax calculator and the LTHR zones calculator with your own numbers.

A worked example

Max heart rate 190, running lactate-threshold heart rate 170 (threshold typically sits around 88–92% of max).

%HRmax Zone 2 = 60–70% of 190 = 114–133 bpm

LTHR Zone 2 (running) = 85–89% of 170 = 145–151 bpm

About 30 beats apart. Neither is wrong.

"Zone 2" means three different things

Three popular systems each have a "Zone 2," and they do not line up:

1. The famous easy "Zone 2": the fat-burning, conversational, longevity-podcast Zone 2. Easy aerobic effort below your first lactate threshold (LT1). In a 5-zone %HRmax model that is Zone 2 (60–70%).
2. Friel's LTHR Zone 2: aerobic endurance just below threshold, between LT1 and LT2. Harder than the easy Zone 2 above. In Friel's system all easy work is Zone 1 (under ~84% of LTHR).
3. The 3-zone model's "Zone 2": the middle "gray zone" between LT1 and LT2, harder still.

So the easy effort everyone means by "do more Zone 2" is %HRmax Zone 2 ≈ Friel Zone 1. On LTHR zones, training "Zone 2" puts you in Friel's endurance band, too hard for the easy session you intended. That mismatch explains a lot of "why do I feel wrecked from easy runs?" See LT1, LT2 and LTHR explained.

The shortcut: LTHR Zone 2 ≈ %HRmax Zone 3

Your everyday endurance run lands at almost the same heart rate in both systems:

• %HRmax: Zone 3 (70–80% of max).
• LTHR: Zone 2 (85–89% of LTHR).

From the example above, %HRmax Zone 3 is 133–152 bpm and LTHR Zone 2 is 145–151 bpm. Hence "Zone 2 is Garmin's Zone 3." %HRmax splits easy work into Z1 + Z2. LTHR puts all easy work in Z1 and starts Z2 at endurance pace.

If you're on a Garmin (or any default-%HRmax watch)

Your watch can build zones from %HRmax, %heart-rate reserve or LTHR. Switch the basis and every bpm range moves, but the zone numbers and colours stay the same. Your easy run that sat in green Zone 2 may now read Zone 1.

• The default is %HRmax. There is no special "Garmin zone system." Polar and many coaches use the same method.
• Garmin labels runs by purpose. "Recovery" and "Base" cover easy and endurance work. "Tempo", "Threshold" and "VO2max" cover the hard stuff. A "Base" run targets roughly 75% of max, the %HRmax-Zone-3 / LTHR-Zone-2 band.
• For suggested workouts, chase the bpm target, not the zone. Hit Garmin's heart-rate target and the zone number does not matter.
• Garmin's threshold estimate is tied to your max. Garmin puts lactate threshold near 90% of maximum heart rate for a well-trained runner (lower for beginners). So the two systems describe nearly the same bpm ranges, and switching changes labels more than targets.

How to resolve it for good

• Chase the effort, not the zone number. Easy aerobic work is conversational: full sentences, ideally nose breathing. The talk test beats any label.
• Know which system your watch is set to. On LTHR/Friel zones, easy days are Zone 1 and Zone 2 is endurance. On %HRmax, easy is Zone 2.
• Pick one system and learn its zones. Do not mix a coach's %HRmax "Zone 2" cue with an LTHR-configured watch. Compare systems on the heart-rate zone models page.
• Anchor to threshold if you can. LTHR zones move with your physiology, not with an age formula. Friel's 30-minute LTHR test gets you the number. His Zone 1 is the easy one.

For what easy aerobic training is and how much to do, see Zone 2 heart rate, explained.

Sources

• Joe Friel, the LTHR-based zone model and the 30-minute field test
• The %HRmax five-zone bands follow the conventional 50–60–70–80–90–100% boundaries
• Garmin's heart-rate health science (lactate threshold near 90% of maximum heart rate)
• r/Garmin PSA on zone confusion