Why LTHR beats %HRmax
Lactate-threshold heart rate (LTHR) is the heart rate at your lactate threshold, roughly the hardest pace you could sustain for an hour. Anchoring zones to it, rather than to an age-estimated maximum, ties your training directly to a meaningful physiological marker you can actually measure.
Joe Friel and Andrew Coggan popularised LTHR zones for endurance athletes. The bands differ slightly between cycling and running because threshold heart rate is sport-specific, running LTHR usually sits a few percent higher.
Reading the seven zones
Zone 1 is active recovery; Zone 2 builds aerobic endurance; Zone 3 is tempo. Zone 4 sits right at threshold (94–99% LTHR for cycling, 95–99% for running), sustainable hard work. Zones 5a, 5b and 5c break the top end into VO₂max, anaerobic capacity and neuromuscular efforts.
Because these zones are pinned to threshold, they stay valid even as your maximum heart rate estimate drifts. Re-test LTHR every few months or after a clear fitness change.
The 30-minute LTHR field test (Friel protocol)
Test solo, on flat terrain or a trainer, when rested. The goal is a steady, maximal 30-minute effort, pace it like a hard time trial, not a sprint start.
- 1
Warm up
Ride or run easy for 10–15 minutes with a couple of short pickups.
- 2
Start the 30-minute time trial
Begin a hard, evenly-paced 30-minute solo effort as if racing. Don't start too fast.
- 3
Press lap at 10 minutes
Ten minutes in, hit the lap button so your monitor averages the final 20 minutes separately.
- 4
Read your LTHR
Your lactate-threshold heart rate is the average heart rate of those final 20 minutes.
Worked example
A cyclist with a tested LTHR of 165 bpm:
| Zone 2, Endurance (81–89%) | 134–147 bpm |
| Zone 3, Tempo (90–93%) | 149–153 bpm |
| Zone 4, Threshold (94–99%) | 155–163 bpm |
| Zone 5a, VO₂max (100–102%) | 165–168 bpm |
Frequently asked questions
How do I find my LTHR?
Do a 30-minute solo time trial at a hard, even effort. Press lap 10 minutes in; your lactate-threshold heart rate is the average heart rate over the final 20 minutes. Test when rested, and repeat separately for cycling and running because threshold heart rate differs between the two.
Is LTHR the same as maximum heart rate?
No. Lactate-threshold heart rate is the rate you can sustain for about an hour, typically 85–92% of maximum for trained athletes. It is a far more useful training anchor than maximum heart rate because it reflects your actual threshold and can be measured directly with a simple field test.
Why are cycling and running LTHR different?
Running generally produces a higher threshold heart rate than cycling for the same athlete, because it recruits more muscle mass and you support your body weight. Test each sport separately; using your cycling LTHR for running (or vice versa) will set one sport's zones noticeably wrong.
How often should I retest LTHR?
Every 4–8 weeks during focused training, or whenever your fitness changes noticeably. Lactate-threshold heart rate shifts with training adaptation, usually your sustainable pace at a given heart rate improves rather than the LTHR number itself moving dramatically.
Sources
- Joe Friel, The Cyclist's / Triathlete's Training Bible. LTHR field-test protocol and %LTHR zone definitions.
- Allen & Coggan, Training and Racing with a Power Meter. LTHR and threshold-based zone framework.