Someone at the café stop keeps telling you to train by heart rate. Your training plan does too. You glance at the strap on the table and then at the heart rate number on your bike computer, and you wonder whether this is real training or just another number to worry about.
Is a heart rate monitor for cycling a training tool or another gadget? We’ll walk through who genuinely benefits from one, what it gets wrong, the free alternative that already works, and which kind to buy if you decide to bother.
What a Heart Rate Monitor Actually Tells You
Wind and hills make speed a liar. The same ride can feel easy with a tailwind and brutal into a headwind, even when the speedometer says the same thing.
Heart rate shows what the ride costs your body. That’s what speed can’t tell you.
💡 I like them. They’re a good indicator of how hard you’re working. Power meters are good for absolute real-time numbers; heart rate is good for telling you how your body is coping (or not!) very soon after the effort.
A power meter reacts the moment you push. Heart rate takes roughly a minute to catch up with a change in effort, because it’s measuring your body’s response rather than the force at the pedal. We want to know whether the whole ride is asking too much, not whether this exact second is hard.
You don’t need a power meter to train with structure. A lactate-threshold heart rate (LTHR) test gives you the heart rate version of FTP, and that’s where heart rate compares to FTP most directly.
So the number has a job. Does training by it actually beat riding by feel?
Does Training by Heart Rate Beat Riding by Feel?
A small study put recreational cyclists through interval training guided by heart rate or power, and both groups improved the same 12.4-mile (20 km) time trial by about 8%. The cheap strap worked as well as the expensive gadget. A similar study in well-trained cyclists found the same pattern.
The free alternative works too. The talk test lines up with the first training threshold: when conversation first becomes uncomfortable, you’re near the boundary where easy riding ends.
The talk test has one weakness. A running study found heart rate kept newcomers closer to target intensities than feel did, though fitness gains were similar.
You may have heard of the 75% rule or the 80% rule. Both are rules of thumb for keeping most of your riding easy, not laws.
Keep most of your riding in that chatty, steady zone. A strap makes it harder to cheat, because it turns “that felt easy” into a number.
👍 I use zones when it feels right. Sometimes I don’t look at all, particularly on social rides.
The strap’s real job is keeping easy rides easy. That job matters most in two places: long climbs and hot days.
Where It Earns Its Keep: Climbs and Hot Days
A long climb exposes every rider who starts too hard. On a climb like that, burning matches at the bottom means surviving the top instead of riding it.
⛰️ I make sure I don’t go deep into the red on a climb. So I go no more than, say, 90% of my maximum heart rate.
That matches a rule you can use right away: pace long climbs by heart rate, not by hope. The number lags on a short ramp, so this matters most on climbs that take several minutes.
Heat and dehydration change the picture through cardiac drift. At the same effort, your heart rate rises as you heat up or dry out, so the number climbs even when the work stays the same.
In one study, trained cyclists rode for two hours at 91°F (33°C), and heart rate rose with dehydration in step with how much fluid they lost. On a hot day, a climbing number at the same pace is your body reporting the cost of the heat. Your fitness hasn’t gone anywhere.
🔥 Heat in particular pushes up my heart rate quite significantly. It’s quite amazing really, by about 5 to 10% in extreme heat.
So when the number climbs at the same pace, back off and drink. Riding hot days by heart rate gives you a simple early warning.
All of that depends on knowing your actual max.
Why Your Max Heart Rate Number Is Probably Wrong
Your max heart rate is the highest your heart will beat in an all-out effort. Training zones are set as percentages of that max, so a wrong max shifts every zone. The old 220-minus-age formula feels precise, but it’s only a guess.
In a 2013 study of 762 sedentary adults aged roughly 16 to 65 on cycle tests, the age-based predictions typically missed measured max by about 11 to 12 bpm. Some individuals were off by 40 bpm or more.
The Tanaka formula, 208 minus 0.7 times your age, is a smarter estimate.
But treat even that as a starting point. Your heart rate zones need a measured max or an LTHR field test to fit you properly. Some coaches simply call it your threshold heart rate.
So is 170 bpm bad? It depends on your own max.
One rider’s 170 bpm is a hard effort, and another rider’s 170 bpm is an easy pace, because max differs from rider to rider. How you feel and whether you can talk matter more than any single number. A number arriving with symptoms that feel wrong is a different matter, and we’ll come back to it.
Even a good max only helps if the sensor is reading the right number.
Chest Strap, Armband or Watch?
Your wrist sensor is handy, and on the bike it can quietly read low. In a 2020 review of 44 studies, wrist sensors under-read during cycling by about 4.5 bpm on average. A 2017 lab test found a chest strap matched ECG most closely, while some wrist devices failed on the bike.
For the clean signal, a chest strap wins because it reads the heart’s electrical activity. An optical armband is the comfortable middle, and a wrist watch is a convenient approximation.
❤️ I ride with a chest strap.
A dedicated strap or armband runs roughly $30 to $105. Models include the Polar H10, Garmin HRM 200, Wahoo Trackr, Polar Verity Sense and a COROS armband. Which is best depends on whether you want maximum accuracy or maximum comfort.
Some Garmin watches, including the Forerunner 965, can broadcast wrist heart rate to a bike computer. If you already own the watch, that’s an easy way to see whether the number changes how you ride before buying another sensor. A bike computer makes the number visible while you’re riding.
But there’s one situation where none of them should rule your ride.
When Not to Trust the Number
A heart rate monitor is a training tool, not a heart test.
Some medications pull the number down even when the effort feels the same. A beta blocker can do that, and the reading stops tracking your effort.
In a 2025 study, healthy volunteers given a single beta-blocker dose had heart rates about 36 bpm lower at the same perceived effort.
If you take beta blockers, zones built on a normal max no longer fit. Ride by effort and the talk test, and ask your doctor for a ceiling. Riders on a beta blocker who are riding with AFib follow the same effort-first rule.
The same caution applies to smartwatch heart alerts. In the Apple Heart Study of more than 400,000 people, researchers warned that a missing alert doesn’t rule out a problem, and an alert on its own isn’t proof of one. Chest pain, dizziness, unusual breathlessness or a racing irregular pulse means stop and see a doctor, whatever the number says.
So where does that leave you?
The Bottom Line: Should You Buy One?
You came here for a clean answer, so here it is.
Buy one if you train for an event like a century, want easy rides to stay easy, pace long climbs, or ride in hot conditions. For those jobs, a chest strap is the cheapest useful training tool you can add. A power meter only pulls ahead for sprints and short, hard efforts, where heart rate can’t react fast enough.
Skip it for now if you ride for fun and conversation, and you can pass the talk test.
If that’s you, leave the numbers at home at least most of the time. One no-numbers ride a week is healthy whether or not you buy a strap.
On a beta blocker, effort beats the number.
Try the free version for a week. Ride your usual easy loop at talk-test pace.
If your “easy” rides keep turning into hard ones, that’s your answer: an inexpensive chest strap is the fix. If they stay easy, you just saved $30.
Know a rider who swears by feel? Share this with them👇
