The WattPlan Podcast · Episode 12 · 9 min
How do you set heart rate zones, and when do you trust them?
Next episodes: What are power zones actually for? · Is Zone 2 worth the hours? · What is cardiac decoupling telling you?
Read the transcript
James. Hello and welcome to the WattPlan Podcast. I'm James. Between family life, the day job, the odd podium and building WattPlan, I read far more sports science than anyone sensible would. This week, the gadget nearly every rider already owns. How do you actually set heart rate zones, and when should you trust them over power? Lyra, our AI research voice, has been through the papers, and every study is linked in the show notes.
Lyra. From your threshold, not your maximum. Threshold heart rate is the highest heart rate you can hold through a long, hard, steady effort, and WattPlan sets five zones as a share of that number. And heart rate is brilliant for steady riding and too slow for anything short and sharp.
James. Threshold, not max? Everyone I know just does two hundred and twenty minus their age.
Lyra. And that formula is a population average. For one rider it can be ten to twenty beats out either way, which is enough to put an endurance ride in the wrong zone. Even a true maximum doesn't tell you where your threshold sits. Two riders with the same maximum can have quite different thresholds, and threshold is what the zones hang off.
James. Give me the zones in plain numbers, then.
Lyra. Take a threshold heart rate of 160 beats. Zone 1, recovery, is anything under 68 percent of it, so below about 109. Zone 2, endurance, is 69 to 83 percent, about 110 to 133. Zone 3, tempo, runs up to 94 percent, about 150. Zone 4, threshold, is 95 to 105 percent, roughly 152 to 168. Above that is Zone 5.
James. Why those percentages, though? They look oddly specific.
Lyra. They're the heart rate match for the power zones. Endurance on power is 56 to 75 percent of FTP, and the heart rate that goes with it is 69 to 83 percent of threshold. So endurance means the same thing in watts and in beats, and WattPlan uses that one scale in the player, on your bike computer and in the Coach.
James. So how do I find my threshold heart rate without a lab?
Lyra. A thirty minute test. Ten minutes of warm-up, a few minutes steady, then thirty minutes as hard as you can hold evenly, like a time trial on your own. Your threshold is the average of the last twenty minutes. The first ten are left out because heart rate takes a while to settle.
James. Thirty minutes flat out sounds brutal if you're new to this, though.
Lyra. Then don't start there. If you're new to structured training, start with the talk test. Easy is full sentences, hard is a few words. Pair a heart rate strap, and if you don't know your threshold yet, the app can estimate it at 93 percent of your maximum. It's a start. The thirty minute test beats it, once you're ready.
James. And is that threshold number tied to anything real in the body, or is it just a handy convention?
Lyra. There's a study that gets close. Borszcz and colleagues, 2019, in the International Journal of Sports Physiology and Performance. Fifteen trained cyclists did an FTP test, ninety-five percent of a twenty minute effort, and a series of constant-power rides to find their maximal lactate steady state. That's the hardest effort where lactate in the blood stays level rather than climbing. [2]
James. And did they line up?
Lyra. Closely, on average. The heart rate at FTP came within about one and a half percent of the heart rate at the lactate steady state, and the two tracked each other well. For a single rider, though, the gap could be up to about eight percent either way. So it's a good anchor, not a lab measurement. Small study, trained riders, and a twenty minute test rather than thirty.
James. But surely, if I've got a power meter, power just does all of this better. Why bother with heart rate at all?
Lyra. If you train with power, your targets are watts, and heart rate is your second opinion. Power is instant. Heart rate takes thirty seconds to a minute to catch up with a change in effort, and heat, caffeine, poor sleep and dehydration all push it up.
James. A second opinion on what, exactly?
Lyra. On cost. Power tells you what your legs produced. Heart rate tells you what it took. A normal power with an unusually high heart rate is telling you something. And on long rides there's a pattern called cardiac drift. At steady power, heart rate creeps up over a couple of hours as you warm up and lose fluid.
James. So if my heart rate drifts over my Zone 2 ceiling late in a long ride, I back off. That's the whole point of a ceiling, surely.
Lyra. If you're riding to power, no. Hold the watts and note the drift. Your effort hasn't changed, your heart is just working harder to deliver it. Early in the ride, the ceiling keeps you honest. Late on, a little drift at the same power is normal. A lot of it, say over ten percent, suggests the ride was too hard for your current fitness, or the heat and fluids caught up with you.
James. And the fatigue side. Can a high heart rate tell me I'm overcooked?
Lyra. It's a clue, not a verdict. In 2013 the European College of Sport Science and the American College of Sports Medicine published a joint consensus on overtraining, led by Romain Meeusen. They reviewed the markers people use, hormones, performance tests, psychological tests, biochemical and immune markers, and concluded that none of them meets all the criteria to be generally accepted. [1]
James. Really? So heart rate's no use for fatigue at all.
Lyra. Not on its own, which isn't the same thing. If the lab markers can't settle it alone, one reading on a chest strap can't either. So an odd heart rate is a reason to ask questions. How did you sleep, did you eat enough, is it hot? Then tell the Coach how your legs feel. It reads your heart rate against power and how hard recent sessions felt, alongside what you tell it, rather than any one number.
James. What about riders with no power meter at all? Does a ride on heart rate alone still count for anything?
Lyra. It does. If heart rate is all you've got, WattPlan gives you your sessions by feel, out of ten, with a heart rate range on the long steady steps. And it works out each ride's Load from your heart rate, so an hour at your threshold heart rate counts like an hour at FTP. It needs your maximum, resting and threshold heart rate filled in to do that properly.
James. And for someone who races? That's all sprints and attacks.
Lyra. Which is exactly where heart rate is the wrong tool. Attacks, sprints, VO2max reps, they're over before heart rate catches up, and adrenaline lifts it anyway. So WattPlan never gives a heart rate target above threshold or for anything under five minutes. If you race, where it helps is keeping the easy days genuinely easy, so you arrive at the hard sessions fresh enough to hit the watts.
James. Where do the studies stop being useful here?
Lyra. Sooner than the neat percentages suggest. The FTP study had fifteen riders and a twenty minute test, and the consensus is about overtraining, not everyday zones. Neither one tests whether five heart rate zones beat seven, or exactly where each boundary should sit for you. The percentages are a convention that lines up with the power zones, not a law of nature.
James. So what do I actually do before the weekend?
Lyra. Open You, then Metrics, and fill in your maximum, resting and threshold heart rate. If your threshold is a guess, ride the 30-Minute Heart-Rate Test, under Tests in the library, on a fresh day. And on your next long steady ride, note your heart rate in the first hour and again at the end, at the same effort, and see how far it drifted.
James. Three numbers in Metrics, one hard half hour, and next time my heart rate climbs late in a long ride, I hold the power instead of panicking.
Lyra. Let the watts set the effort and let your heart tell you what it cost. The day those two disagree is the day worth asking why.
Lyra. The full article and every study we mentioned are on the WattPlan blog, linked in the show notes. And if you've enjoyed this, follow the WattPlan Podcast wherever you're listening, so you don't miss the next one.
James. And if you want a plan built around the time you've actually got, get WattPlan on the App Store or Google Play. Thanks for listening.
Voices produced with ElevenLabs. James's voice is a clone of his own, Lyra is an AI voice, and James reviews every episode.
Heart rate zones for cycling are five bands set from your threshold heart rate, the average of the last 20 minutes of a 30-minute effort. Zone 2 runs from 69 to 83% of it. Zones from 220 minus age are less reliable, because that formula underestimates the maximum in older adults, as Tanaka found across 18,712 people in 2001.
What heart rate zone should you cycle in?
Most of your week belongs in zone 2 and the hard sessions in zone 4 and above. The table gives the five zones WattPlan uses, as a share of threshold heart rate, in beats per minute at four thresholds, with the matching power zone and talk test.
| Zone | Share of threshold | Threshold 150 | 160 | 170 | 180 | Power zone | Talk test |
|---|---|---|---|---|---|---|---|
| 1 Recovery | 0-68% | below 103 | below 110 | below 117 | below 123 | 0-55% of FTP | chat freely |
| 2 Endurance | 69-83% | 104-125 | 110-133 | 117-141 | 124-149 | 56-75% | full sentences |
| 3 Tempo | 84-94% | 126-141 | 134-150 | 143-160 | 151-169 | 76-90% | short sentences |
| 4 Threshold | 95-105% | 143-158 | 152-168 | 162-179 | 171-189 | 91-105% | talking is hard |
| 5 VO2 max | 106%+ | 159+ | 170+ | 180+ | 191+ | above 105% | a word at a time |
The talk test column has evidence behind it. A 2008 study in the Journal of Cardiopulmonary Rehabilitation and Prevention lowered the ventilatory threshold in healthy young adults with a blood donation and raised it with training, and the last stage at which people could still speak comfortably moved with the threshold each time. Full sentences means zone 2.
Should you cycle in zone 2 or 3?
Zone 2 for the long ride and the easy days, zone 3 only when the session is built for it. Sweet spot sits across the top of zone 3 and the bottom of zone 4, a planned dose rather than a default. Our guide to zone 2 training covers what the easy days are for.
Is 140 bpm too high for zone 2?
It depends on your threshold. At a threshold of 170, zone 2 tops out at 141, so 140 is the upper edge of endurance. At 160 it tops out at 133, and 140 is tempo. At 180, 140 sits in the middle of zone 2.
Is 220 minus age accurate?
Tanaka, Monahan and Seals pooled 351 studies with 492 groups and 18,712 people in 2001 and found that maximal heart rate fits 208 minus 0.7 times age, the same for men and women and for active and sedentary people. A laboratory check on another 514 people gave 209 minus 0.7 times age, and 220 minus age underestimates the maximum in older adults. Nes and colleagues measured 3,320 healthy men and women in the HUNT fitness study in 2013, keeping only verified maximal efforts, and found 211 minus 0.64 times age with a standard error of 10.8 beats a minute. Earlier formulas underestimated the maximum in people over 30.
| Equation | Evidence | Predicted maximum at 25 | at 40 | at 60 |
|---|---|---|---|---|
| 220 minus age | Not validated with enough older adults, underestimates them | 195 | 180 | 160 |
| 208 minus 0.7 x age | 18,712 people in 351 studies, Tanaka 2001 | 191 | 180 | 166 |
| 211 minus 0.64 x age | 3,320 adults, standard error 10.8 beats, Nes 2013 | 195 | 185 | 173 |
Even the best equation carries a standard error of about 11 beats, so zones built on an age-predicted maximum can be a full zone out. Our view at WattPlan is that zones belong on a tested threshold heart rate, and an age formula is only a placeholder until you have ridden the test. When a rider gives WattPlan a maximum heart rate but no threshold, the app estimates the threshold at 93% of that maximum and marks it as estimated. The Metrics page can also fill in a maximum from your age with 220 minus age, and the same page says a threshold from a hard 30 to 60 minute effort beats an estimate.
How do you find your threshold heart rate?
Ride 30 minutes as hard as you can hold evenly, alone, and take the average heart rate of the last 20 minutes. The first 10 are dropped because heart rate is still climbing. Dumke and colleagues had 10 male cyclists ride a 30-minute and a 60-minute time trial in 2006. Heart rate averaged 90.3% of maximum over the 30 minutes and 84.6% over the hour. The hour tracked the heart rate at the first lactate rise, with a correlation of 0.78, while the 30-minute figure sat near the heart rate at the higher lactate markers, at 91 to 92% of maximum. A 30-minute test gives a threshold near the top of what you can hold, which is what the zones above are built on.
WattPlan's 30-minute heart-rate test is in the workout library for riders with a strap and no power meter, 50 minutes in all. It opens with 10 minutes building gently, with a prompt to check the strap is reading, then 3 minutes steady where you can still talk in full sentences, then 2 minutes easy to settle your breathing. The 30-minute block is a free ride, so a smart trainer is released and you set the effort, ridden as if racing alone, with talking hard throughout. The player takes the average heart rate of the last 20 minutes as your threshold, and the Metrics page marks that number as from your test. A plan without an event date puts this test in its final week when you ride by heart rate, on the first quality slot of 50 minutes or more, so a final week of shorter rides gets no test.
Why does heart rate drift on long rides?
Heart rate rises at a steady power as stroke volume falls, and the rise is larger in heat. Wingo, Ganio and Cureton reviewed the evidence in 2012 and put the onset at about 10 minutes of moderate exercise, with a lower maximal oxygen uptake alongside it, so the higher heart rate reflects a higher relative intensity rather than a strap error. In a 2005 study by Wingo and colleagues, nine male cyclists rode 45 minutes at 60% of VO2max in 35 °C heat. Heart rate rose from 151 to 169 beats a minute between minute 15 and minute 45, a 12% rise, stroke volume fell 16% and VO2max measured straight afterwards was 19% lower.
So a zone 2 ceiling set for the first hour will be breached in the third at the same power. Hold the power and note the drift. Cardiac decoupling turns that drift into a fitness signal.
When should you use power instead?
Heart rate lags an effort by a minute or more, so it cannot pace a 30-second surge or a 3-minute interval. WattPlan gives a heart-rate target only for steady steps of five minutes or longer, and never for a step above threshold. Anything shorter or harder is ridden by feel, with the talk test cues in the table. The same five zones drive the workout player, the targets sent to a Garmin or Wahoo and the Coach, so endurance means the same beats everywhere. Our power zones guide and the FTP calculator cover the seven power zones they map to.
When a ride carries a heart-rate stream and no power, WattPlan works out its Load from the heart rate through the ride, weighting each second more heavily the closer it sits to your maximum, and scaled so an hour at your threshold heart rate counts like an hour at FTP. A ride with power is always scored from power first. That needs your threshold, maximum and resting heart rate, which you set under You, in Metrics. Without the full profile the app scores the ride from your average heart rate against your maximum. Training load without a power meter covers how the two compare.
What to do this week
- Ride the 30-minute test fresh and alone, and take the average of the last 20 minutes as your threshold heart rate.
- Enter threshold, maximum and resting heart rate, then set your zones from the first table rather than from your age.
- Set a zone 2 ceiling for the first hour of your next long ride, then hold the power and let the heart rate drift.
- Use the talk test for anything under five minutes.
- Retest at the end of each block. If a sportive is the goal, the event training plans start from the same threshold.
What we don't know yet
The age equations describe group averages, and the 10.8 beat standard error in the HUNT data means many riders' true maximum sits more than 10 beats from the prediction. We found no study that validates the last 20 minutes of a 30-minute effort as a threshold measure, and Dumke's study had 10 male cyclists. The 2005 drift study had nine men riding in 35 °C, and cooler conditions are unmeasured here. The five zones are a coaching convention, and no study we found has tested the 69 to 83% band against a neighbouring one.
Sources
- Age-predicted maximal heart rate revisited, Journal of the American College of Cardiology
- Age-predicted maximal heart rate in healthy subjects: The HUNT Fitness Study, Scandinavian Journal of Medicine and Science in Sports
- Heart rate at lactate threshold and cycling time trials, Journal of Strength and Conditioning Research
- Cardiovascular drift during heat stress: implications for exercise prescription, Exercise and Sport Sciences Reviews
- Cardiovascular drift is related to reduced maximal oxygen uptake during heat stress, Medicine and Science in Sports and Exercise
- The talk test as a marker of exercise training intensity, Journal of Cardiopulmonary Rehabilitation and Prevention