How to Set Heart Rate Zones From Your LTHR

To set zones from your lactate threshold heart rate (LTHR), you do three things: estimate your LTHR with a hard 30-minute solo effort, multiply that number by a set of percentages to get your zone boundaries, and enter those boundaries in your watch or app. The work is in the first step. The rest is arithmetic. A field test like this gives a training estimate of LTHR; it does not measure blood lactate the way a laboratory test does.

This guide walks through each step for runners and triathletes, shows a worked example, and explains where LTHR zones fit next to zones built from max heart rate. It also covers the limits: threshold zones are a tool, not a verdict on your fitness.

TL;DR

• LTHR is a heart-rate anchor close to the highest effort you could sustain steadily for about an hour. Joe Friel’s solo 30-minute test, averaging the final 20 minutes, is a common field method for estimating it. It is an estimate, not a blood lactate measurement.
• Zones are percentages of that one number. Joe Friel’s running scheme has seven bands, from under 85% of LTHR (Zone 1) to above 106% (Zone 5c). It is not the same as the five-zone max heart rate systems many apps use.
• Cycling percentages differ slightly from running, so set separate zones for each sport profile.
• Treat every number as a starting range. Retest every so often and check zones against how the effort actually feels.

Table of Contents

• What LTHR is and why zones are built on it
• Step 1: Find your LTHR with a 30-minute test
• Step 2: Turn LTHR into zone boundaries
• Step 3: Enter the zones in your watch
• LTHR zones versus max HR zones
• How to use the zones once you have them
• Common mistakes
• Try it with SnapHRZones
• FAQ
• Sources

What LTHR is and why zones are built on it

In the lab, lactate threshold is identified from blood samples taken during a graded test: roughly, the intensity above which blood lactate starts to accumulate instead of staying steady. Labs and researchers use several definitions, so “threshold” can mean slightly different things. In practice you feel it as the point where effort shifts from “hard but controlled” to “this will not last.” LTHR is the heart rate associated with that point. A field test estimates it from heart rate alone; Friel himself calls the result “an approximation of your LTHR.”

Why anchor zones to it? Max heart rate formulas such as 220 minus age are population averages, and individual max heart rate varies widely. According to a coaching comparison of max HR and threshold HR zones, a formula-based max can lead to real errors in intensity, and threshold-based zones are tied to how you actually perform. That is an argument from coaching practice rather than a controlled trial, so read it as a reasonable preference and not a proven rule.

There is also a practical angle. Garmin’s own explanation of lactate threshold says that for experienced athletes it typically sits near 90% of max heart rate, but that this is highly individual and that beginners often find it at a lower percentage. If your threshold sits at, say, 84% of your max, zones that assume a typical percentage will be placed too high for you. Zones built from your own LTHR estimate avoid that particular assumption, although they still depend on how well the test went.

Step 1: Find your LTHR with a 30-minute test

The most widely used field method comes from endurance coach Joe Friel. His description of the LTHR test is simple: go as hard as you can sustain for 30 minutes, alone, and use your average heart rate for the last 20 minutes as your LTHR estimate. He stresses that it must be solo, because doing it in a race or with partners pushes the number too high, and that the first 10 minutes are not an easy warm-up: the whole 30 minutes is one sustained hard effort. Heart rate is still rising during those first minutes, which is why only the final 20 are averaged.

How to run the test

1. Pick the right conditions. A flat road, track or treadmill works best. Avoid big hills, heavy wind, and heat that would inflate your heart rate.
2. Be rested. Do the test on a fresh day, not after a hard block. Fatigue lowers the heart rate you can reach.
3. Warm up. Warm up as you normally would before a hard effort. Friel’s description does not prescribe a specific warm-up.
4. Start a 30-minute effort, alone. Press the lap button at the start and go as hard as you can sustain evenly for the full 30 minutes. Do not start so fast that you fade, and do not watch your heart rate; you are not aiming for a number.
5. At 10 minutes, press lap again. Keep the same effort through minute 30.
6. Read the average. The average heart rate of the final 20 minutes is your LTHR estimate. Use it as is; this protocol does not apply a multiplier.
7. Cool down with easy running.

Use a chest strap if you have one. Wrist sensors can lag or drift during hard efforts, which matters when a few beats shift every zone boundary.

If you want a guided walk-through with a place to record the result, our lactate threshold heart rate calculator and field test page covers the same protocol. It turns your final-20-minute average into an estimated LTHR; it does not calculate Friel’s seven zones, so use the tables below for that step.

Run it for each sport

Heart rate at the same relative effort is not identical across sports. A PubMed study on transferring heart rate recommendations between running and cycling tested 371 people on both a treadmill and a bike and found that heart rate at the lab-defined threshold did not correlate between the two; the authors concluded that a sport-specific test is a prerequisite for reliable heart-rate recommendations. That is one reason triathletes are usually advised to test and set zones separately for running and cycling. If you only have time for one test, run it in your main sport and treat the others as provisional.

What about a watch’s automatic estimate?

Many watches estimate LTHR for you. These estimates can be convenient, but they are not always close. A 2024 PubMed study of one popular watch compared its lactate threshold output with a standardized blood lactate field test, in 26 runners. The watch’s threshold pace was about 12% slower than the field test, while its threshold heart rate was only about 1.7% lower, a difference that was not statistically significant. The authors judged the estimate sufficient for recreational athletes but not for detailed professional training management. One device in one study does not settle the matter, but it is a good reason to check an automatic number against a real test before building a training block on it.

Step 2: Turn LTHR into zone boundaries

Once you have a number, each zone is a percentage band of it. Friel’s quick guide to setting zones lists these running bands. Each band is a percentage of your LTHR estimate:

The same guide gives slightly different cycling bands, with Zone 1 below 81% of LTHR, Zone 2 from 81% to 89%, Zone 3 from 90% to 93% and Zone 4 from 94% to 99%. Zones 5a to 5c use the same percentages as the running bands on that page. (Friel has published slightly different versions of his upper bands over time, so check which version a coach or app is using.) That difference is why you should not copy a running table into a bike profile.

Other schemes exist. Some use five zones, and a Velo guide to heart rate based cycling training uses a five-zone model built on threshold heart rate, with Zone 1 under 68% and Zone 2 at 69% to 83%. Different percentages are not a contradiction. Each coach draws the lines differently, and the zones are conventions rather than physiological walls. Pick one scheme and stay with it long enough to learn what each zone feels like.

A worked example

Say a runner’s 30-minute test gives an estimated LTHR of 168 bpm. Using the running bands above, we apply one rounding rule throughout (our own arithmetic): each zone starts at 168 × its lower percentage, rounded to the nearest whole beat, and ends one beat below where the next zone starts. Zone 5c starts above 106%, so it begins one beat after 168 × 1.06 (178.08, rounded to 178).

Zone starts before rounding: 142.8 (85%), 151.2 (90%), 159.6 (95%), 168 (100%), 173.04 (103%) and 178.08 (106%). Friel’s published bands leave small gaps (for example between 89% and 90%); letting each zone run up to the next one closes them, so every whole beat belongs to exactly one zone. Rounding can move a boundary by up to half a beat, which is far smaller than normal day-to-day variation.

Notice how narrow Zones 2 to 4 are: only a handful of beats each. That is normal for threshold-based schemes, and it is also why heart rate drift, heat or a poor night of sleep can push you across a boundary without any real change in effort.

Pace zones as a companion

Heart rate lags behind effort, so it is a poor guide for short intervals. Many runners pair LTHR zones with pace targets for track work. A running pace and race time calculator (in Spanish, with min/km output) can help you translate a recent race result into pace per kilometer, which you can convert to miles.

Step 3: Enter the zones in your watch

The exact menu path depends on the device, but the principle is the same everywhere: switch the zone basis from max heart rate to a percentage of LTHR, then enter your number.

On a Garmin watch, the heart rate zone settings in the owner’s manual explain that you can set separate zones for each sport profile, such as running, cycling and swimming. Another Garmin manual notes that you can choose to view and edit zones as a percentage of lactate threshold heart rate, then enter your LTHR.

A reliable routine:

1. Open the heart rate zone settings for your running profile.
2. Change the basis to the LTHR option.
3. Enter your tested LTHR.
4. Compare the boundaries the watch produces with your own table. Garmin’s LTHR-based presets use five zones with their own percentages, which may differ from Friel’s seven-band scheme. You can edit individual boundaries manually if you want them to match.
5. Repeat for the cycling profile with its own test result.

For a device-specific walkthrough, including Zone 2 targets, see our guide to Garmin heart rate zones.

LTHR zones versus max HR zones

Neither is perfect. Max HR zones are easy and fine for general fitness. LTHR zones take one hard effort and tie your boundaries to an estimate of your own threshold. SnapHRZones’ main calculator uses a five-zone max heart rate system; it does not convert LTHR into Friel’s bands. If you are not ready for a hard 30-minute test, you can start with our heart rate zone calculator, which uses max heart rate with optional resting heart rate, and switch to LTHR zones later.

How to use the zones once you have them

Setting zones is the easy part. A few habits keep them useful.

• Easy means easy. Most of your running volume sits in Zones 1 and 2. Many runners drift into a middle band where every run is moderately hard. If you are curious about that middle range, our piece on Zone 3 training for runners and cyclists explains when it can be useful.
• Use Zones 4 and 5 sparingly. These support threshold and interval sessions. Garmin’s article describes threshold-focused training as a way to work on raising lactate threshold.
• Mix in effort by feel. An American Heart Association News article notes that many factors, including exertion and stress, affect heart rate, and quotes a cardiologist who is not a fan of fixating on heart rate: she wants exercisers to be able to say a full sentence without gasping. If a “Zone 2” run feels hard on a bad day, trust the feeling and slow down.
• Retest. Fitness changes, so your LTHR can too. Many coaches suggest retesting every several weeks to a few months or after a block of focused training. There is no single right interval, so use your training cycle as a guide.
• Keep running-specific zones for running. Our heart rate zones for running guide goes deeper on how runners apply them across easy runs, tempo work and long runs.

Common mistakes

Starting too fast. If you burn your legs in the first five minutes, your final 20-minute average will be low and your zones will sit too low.

Testing when tired or overheated. Heat raises heart rate for a given pace, and fatigue can lower the maximum you can reach. Either one skews the result.

Mixing sports. A running LTHR does not carry over cleanly to the bike, as the running-versus-cycling research above suggests.

Chasing the number. A heart rate zone is a range, not a target to hit to the beat. If you want a related primer on why day-to-day readings move, we cover it in heart rate versus HRV.

Using zones with medical conditions unchecked. If you have a heart condition, take medication that affects heart rate, or have symptoms such as chest pain or unusual breathlessness during exercise, talk to your doctor before a maximal or near-maximal test.

Try it with SnapHRZones

SnapHRZones is a free heart rate zone calculator with science-based formulas, gender-specific options and optional resting heart rate input. Use it for a quick baseline, then compare it with your LTHR zones after your field test. Open the calculator and see where your numbers land.

FAQ

What percentage of LTHR is Zone 2?

It depends on the scheme. In Friel’s running bands, Zone 2 is 85% to 89% of LTHR (81% to 89% on the bike), while the Velo five-zone model cited above uses 69% to 83%. A Zone 2 defined as a percentage of max heart rate is a different thing again. Check which scheme your app or coach uses before comparing numbers.

Can I set zones from LTHR if I don’t know my max heart rate?

Yes. That is one advantage of the method, since the zones are percentages of LTHR alone. Many devices still ask for a max heart rate for other features, such as calorie estimates, so enter a sensible value if you have one.

How do I find LTHR without a lab test?

The common field method is Friel’s solo 30-minute test, using the average heart rate of the final 20 minutes. It estimates LTHR from heart rate; it does not measure blood lactate, so treat the result as a working number and adjust if the zones feel consistently off.

Are threshold heart rate zones better than max HR zones?

For performance-focused training many coaches prefer them, because they tie to your own threshold rather than a formula. For general fitness or a first attempt at heart rate training, max HR zones are simpler and still useful.

This guide is for general education. A sustained 30-minute hard effort is vigorous exercise; if you are unsure whether it is appropriate for you, talk to a healthcare professional first.

Sources

• Determining your LTHR, Joe Friel
• A Quick Guide to Setting Zones, Joe Friel’s Blog
• Heart Rate Zones: Maximum HR or Threshold HR?, Kinetic Sports
• What’s Your Lactate Threshold & How Can You Train With It?, Garmin
• Setting Your Heart Rate Zones, Garmin fenix 7 manual
• Setting Your Heart Rate Zones, Garmin Instinct Crossover manual
• Heart-rate recommendations: transfer between running and cycling exercise, PubMed
• Garmin Fenix 7 underestimates performance at the lactate threshold, PubMed
• Heart-Rate Based Cycling Training Guide, Velo
• Watch your heart rate, but don’t obsess about it, American Heart Association

Recommended

• Garmin Heart Rate Zones: How to Set 5 Zones and Train Zone 2
• Lactate Threshold Heart Rate Calculator | LTHR Field Test