Joe Friel's zones anchor to your lactate threshold heart rate (LTHR), not your age or resting heart rate. Enter your tested LTHR to get all 7 training zones instantly.
Don't have an LTHR number yet? Scroll down for the 30-minute test that finds it.
Friel's percentage cutoffs differ between cycling and running for zones 1 through 4.
LTHR Used
--bpm
Zone 4 Range
--bpm
Your Friel LTHR training zones
These zones are anchored to a tested lactate threshold. For zones built from resting and max heart rate instead, try the Karvonen calculator.
What Is LTHR?
Lactate threshold heart rate (LTHR) is the heart rate at which lactate starts building up in your blood faster than your body can clear it. Below this point, effort feels sustainable for a long time. Cross it, and fatigue builds fast. Joe Friel, a coach who has trained cyclists and triathletes for decades and wrote The Cyclist's Training Bible and The Triathlete's Training Bible, built his entire zone system around this single number instead of around age or resting heart rate.
Because LTHR reflects your actual fitness on the day you test it, Friel's zones adjust as you get fitter. Your max heart rate barely changes over a training cycle. Your LTHR does, which is part of why competitive cyclists and runners retest it every 6 to 8 weeks.
How to Test Your LTHR
Friel's own protocol is a 30-minute solo time trial, done at the hardest sustainable effort you can hold for the full 30 minutes. At the 10-minute mark, hit the lap button on your heart rate monitor. When you finish, check your average heart rate for the last 20 minutes. That number approximates your LTHR.
30-min time trial, average HR of the final 20 minutes = 165 bpm → LTHR = 165 bpm
This test is demanding. It only works if you genuinely pace it as an all-out 30-minute effort, not a comfortable ride. Go out too hard and fade, or hold back and never approach threshold, and the number won't reflect your real LTHR. A lab lactate test or a recent hard race result near threshold effort (a 10-mile time trial for cycling, a hard 10K for running) is a reasonable cross-check if your number seems off.
Friel's 7 Heart Rate Zones
Both tables use the same 7-zone structure. Only the percentage cutoffs for zones 1 through 4 differ between cycling and running. Zones 5a, 5b, and 5c, the 3 hardest bands, use identical percentages for both sports.
Cycling (example LTHR 165 bpm)
Zone
% of LTHR
Example (LTHR 165)
Zone 1 (Recovery)
< 81%
< 134 bpm
Zone 2 (Aerobic)
81–89%
134–147 bpm
Zone 3 (Tempo)
90–93%
149–153 bpm
Zone 4 (SubThreshold)
94–99%
155–163 bpm
Zone 5a (SuperThreshold)
100–102%
165–168 bpm
Zone 5b (Aerobic Capacity)
103–106%
170–175 bpm
Zone 5c (Anaerobic Capacity)
> 106%
> 175 bpm
Running (example LTHR 165 bpm)
Zone
% of LTHR
Example (LTHR 165)
Zone 1 (Recovery)
< 85%
< 140 bpm
Zone 2 (Aerobic)
85–89%
140–147 bpm
Zone 3 (Tempo)
90–94%
149–155 bpm
Zone 4 (SubThreshold)
95–99%
157–163 bpm
Zone 5a (SuperThreshold)
100–102%
165–168 bpm
Zone 5b (Aerobic Capacity)
103–106%
170–175 bpm
Zone 5c (Anaerobic Capacity)
> 106%
> 175 bpm
Zones 1 and 2: Easy Effort
Zone 1 is recovery, easy enough that it barely counts as training stress. Zone 2 is aerobic base work, the pace you can hold for hours while still talking in full sentences. Most weekly training volume belongs here.
Zone 3: Tempo
Zone 3 sits in an awkward middle ground: moderately hard, but not hard enough to drive real threshold adaptations. Friel and most coaches recommend limiting time here rather than building a training plan around it.
Zone 4: SubThreshold
Zone 4 sits below LTHR itself. This is classic tempo and cruise-interval territory, sustainable for 20 to 40 minutes with focused effort. It's one of the most direct ways to raise your threshold over time.
Zones 5a, 5b, and 5c: Above Threshold
Zone 5a sits right at and slightly above LTHR, the pace of a hard 20-minute effort. Zone 5b pushes into VO2 max territory, reserved for shorter, harder intervals. Zone 5c is short, maximal, anaerobic work: 30 seconds to 2 minutes at a time, with real recovery between efforts. Plan downtime after any of the 3.
Why Cycling and Running Zones Differ
Running recruits more muscle mass and carries more impact stress than cycling at the same relative effort, which pushes running heart rate higher for a given intensity. That's why Friel's running zones 1 through 4 sit a few percentage points higher than the equivalent cycling zones. Zones 5a, 5b, and 5c use identical percentages for both sports, since both are already anchored close to LTHR itself, where the sport-specific gap narrows.
Practically, this means you can't reuse a cycling LTHR to calculate running zones, or vice versa. Test each sport separately, and expect a noticeably higher LTHR number from a running time trial than from a cycling one, even if your overall fitness is identical.
Friel vs. Karvonen: Which Should You Use?
Friel's LTHR method and the Karvonen method both build zones from a real physiological number instead of guessing off your age, but they anchor to different things. Karvonen uses heart rate reserve (max HR minus resting HR). Friel uses your lactate threshold directly.
If you're training seriously for a specific cycling or running goal and are willing to do a real threshold test, Friel's zones are more precise for that sport. If you want one general zone system across whatever activity you're doing that day, without a hard 30-minute test, the Karvonen calculator is the simpler starting point.
Frequently Asked Questions
Common questions about LTHR testing and Friel's zone system.
LTHR stands for lactate threshold heart rate, the heart rate at which lactate starts building up in your blood faster than your body can clear it. Joe Friel, a longtime cycling and triathlon coach, built his 7-zone training system entirely around this number instead of age-based max heart rate or resting heart rate.
Friel's protocol is a 30-minute solo time trial at the hardest pace you can sustain for the full 30 minutes. Click the lap button on your heart rate monitor at the 10-minute mark, then check your average heart rate for the final 20 minutes. That average approximates your LTHR.
Zones 5a, 5b, and 5c split what other systems treat as a single top zone into 3 distinct efforts: SuperThreshold (5a), Aerobic Capacity or VO2 max work (5b), and Anaerobic Capacity (5c). Each drives a different physiological adaptation and needs a different amount of recovery.
No. Zones 1 through 4 use different percentage cutoffs for cycling versus running, since running produces a higher heart rate than cycling at the same relative effort. Zones 5a, 5b, and 5c use identical percentages for both sports. Always test LTHR separately for each activity.
It's widely used in cycling and running coaching and is reasonably reliable if paced correctly, genuinely all-out for the full 30 minutes. A lab lactate test or a recent hard race result near threshold effort is a good cross-check if your number seems off.
Use Friel's zones if you're training seriously for cycling or running and willing to do a real threshold test. Use the Karvonen method if you want one simpler zone system that only needs your resting and max heart rate.
Every 6 to 8 weeks during a structured training block is a common guideline, since LTHR shifts as your fitness changes. Retesting after a big jump in training volume or a long break keeps your zones accurate.
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Want Zones Without a Time Trial?
The Karvonen method combines your resting heart rate with your max heart rate, no 30-minute test required.
