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

If you set your watch to LTHR-based zones and noticed your Zone 2 is a good 20–30 beats higher than it was with the old percent-of-max zones, nothing is broken and your fitness hasn't changed. You've just discovered that "Zone 2" isn't one fixed thing. It's a label, and different zone systems pin that label to different intensities. This is one of the most common heart-rate mix-ups (a Garmin-subreddit PSA about it went viral for a reason). Here's why it happens and how to make it stop confusing you.

The short answer

The two systems measure your zones against different reference points and carve the range up with different percentages:

• %HRmax zones anchor everything 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, a number much closer to the top of your range. In the running version, Zone 2 is 85–89% of LTHR.

Because Friel's Zone 2 is a high percentage of a high anchor, it lands at a higher absolute heart rate than 60–70% of your max. Same name, different intensity. Plug your numbers into both the %HRmax calculator and the LTHR zones calculator, and you'll see the gap yourself.

A worked example

Say your max heart rate is 190, and your running lactate-threshold heart rate is 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

That's the "quite a bit higher" you noticed, about 30 beats. Neither is wrong. They're answering different questions.

The real trap: "Zone 2" means three different things

Here's the bit nobody tells you. At least three popular systems each have a "Zone 2," and they don't line up:

1. The famous easy "Zone 2": the fat-burning, conversational, longevity-podcast Zone 2. Physiologically this is your easy aerobic effort, sitting below your first lactate threshold (LT1). In a 5-zone %HRmax model that's roughly Zone 2 (60–70%).
2. Friel's LTHR Zone 2: this is aerobic endurance just below threshold, sitting between LT1 and LT2. It's meaningfully harder than the easy Zone 2 above. In Friel's system, all of your genuinely easy work is Zone 1 (everything 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 aerobic effort everyone means when they say "do more Zone 2" is %HRmax Zone 2 ≈ Friel Zone 1. If your watch is on Friel/LTHR zones and you go train "Zone 2," you'll be in his endurance band, too hard for the easy session you intended. That single mismatch is behind a huge share of "why do I feel wrecked from easy runs?" confusion. For the underlying landmarks, see LT1, LT2 and LTHR explained.

The shortcut that resolves it: LTHR Zone 2 ≈ %HRmax Zone 3

Here's the practical punchline. Your everyday endurance run, the bulk of your training, comes out at almost the same heart rate in both systems. Only the label changes:

• In %HRmax zones it's Zone 3 (70–80% of max).
• In LTHR zones it's Zone 2 (85–89% of LTHR).

With the numbers from the example above, %HRmax Zone 3 is 133–152 bpm and LTHR Zone 2 is 145–151 bpm, essentially the same band. That's why experienced runners say "Zone 2 is Garmin's Zone 3." So your LTHR Zone 2 isn't reading high by mistake. It's high because it lines up with %HRmax Zone 3, not Zone 2. The systems just count the easy end differently: %HRmax splits your easy work into Z1 + Z2, while LTHR lumps all the genuinely easy stuff into Z1 and only starts Z2 at your 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, and you pick the basis in settings. When you switch the basis, every zone's bpm range moves, but the zone numbers and colours stay the same, so "Zone 2" looks identical while secretly representing a different intensity. Change the setting and your easy run that used to sit in green Zone 2 might now read as Zone 1. It feels like the goalposts moved, but you just changed the ruler. A few specifics worth knowing:

• The default is %HRmax. There's no special "Garmin zone system." Out of the box it's percent-of-max, the same mainstream method Polar and plenty of coaches use, and it's perfectly fine for most runners.
• Garmin labels runs by purpose, not just number. "Recovery" and "Base" cover your easy and endurance work; "Tempo", "Threshold" and "VO2max" cover the hard stuff. A "Base" run (your bread-and-butter endurance session) targets roughly 75% of max, i.e. that %HRmax-Zone-3 / LTHR-Zone-2 band again.
• For suggested workouts, chase the bpm target, not the zone. Garmin's daily suggested workouts hand you a specific heart-rate target with a range. Hit the target and it doesn't matter what zone number lights up. The target is the thing.
• Garmin's own threshold estimate is tied to your max. Garmin notes that lactate threshold usually sits around 90% of maximum heart rate for a well-trained runner (lower for beginners). Because threshold is pinned near your max, the LTHR and %HRmax systems end up describing nearly the same bpm ranges, which is exactly why switching between them changes the labels far more than the actual targets.

How to resolve it for good

• Stop chasing the zone number; chase the effort. Easy aerobic work is conversational: you can speak in full sentences, ideally breathe through your nose. That's true whether your watch calls it Zone 1 or Zone 2. The talk test beats any label.
• Know which system your watch is set to. If it's LTHR/Friel zones, your easy days live in Zone 1, and Zone 2 is endurance/tempo, not the easy stuff. If it's %HRmax, easy is Zone 2.
• Pick one system and learn what its zones mean. Don't mix a coach's %HRmax "Zone 2" cue with an LTHR-configured watch. Consistency matters more than which system you choose. Compare how each one carves up the range on the heart-rate zone models page.
• Anchor to threshold if you can. LTHR zones are more individual than %HRmax (they move where your physiology changes, not where a generic age formula guesses your max). Friel's 30-minute LTHR test gets you the number. Just remember his Zone 1 is the "easy" one.

The numbers aren't contradicting each other. They're two maps of the same terrain at different scales. Once you know which map you're holding, the easy days get easy again. For the deep dive on what easy aerobic training actually is and how much to do, see Zone 2 heart rate, explained.

Sources

Joe Friel, on 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 note that lactate threshold typically falls near 90% of maximum heart rate comes from Garmin's heart-rate health science. This post was prompted by a widely shared r/Garmin PSA on zone confusion.