Are Heart Rate Monitor Watches Accurate?

EndurElite Chief Endurance Officer Matt Mosman discusses if watches that measure heart rate on the wrist are accurate.

Do Heart Rate Monitor Watches Work?

Don't break my heart, my achy breaky heart. I just don't think he'd understand.

Oh, Billy Ray Cyrus, how I envy your sweet Mississippi mudflap mullet and your velvety vocals, but what the hell happened to your daughter? My goodness.

Maybe for my next video intro, I'll come swinging in on a wrecking ball in my underpants.

Well, enough of that. Matt Mosman here hitting you with another endurance fast fact. So what does Billy Ray Cyrus have to do with the fast fact for today?

Well, in the spirit Valentine's Day, we are gonna talk about heart rate training.

More specifically, we're gonna talk about devices like this Garmin here that measure heart rate on your wrist. And even more specifically than that, we are gonna tell you if these are accurate or if they are not.

So since we're not "bros" over here at EndurElite, we should make a t-shirt actually with that, like, "EndurElite: We Don't Do 'Bro'." We actually rely on the science.

So there was an actual research study done on the accuracy of various watches that measure heart rate from the wrist.

Heart Rate Monitor Watches That Were Tested:

And as a bonus material today, I have actually tested the accuracy of my Garmin. So let's jump into the study that looked at the accuracy of these various watches.

The research

So what the researchers did in this study is they took 50 people and stuck them on the dreadmill, I mean treadmill, and had them walk at 2 miles-per-hour up to running at 10 miles-per-hour for about 30 minutes.

And what they did to all these subjects is they hooked them up to actually four different things.

  • They had them wear a typical heart rate chest strap.
  • They hooked them up to an EKG, which is a medical device that is 100% accurate when it comes to measuring heart rate.
  • And then they had them wear one device on their right wrist and another device on their left wrist that measured heart rate from there.

So you might have the Apple Watch on this wrist and then the Fitbit Surge on this wrist.

EKG and straps that measure heart rate from the chest are the most accurate

So they sent them through the study, and at the end of the study, this is really surprising actually, they found compared to the EKG and the heart rate strap, which were all basically aligned so if the EKG read, you know, 160 beats-per-minute, and they found that the Polar or the heart rate chest strap was also measuring the same.

But what they found with the devices that measured heart rate on the wrist is that heart rate was off by an astounding 29 to 39 beats-per-minute.

That's a hell of a lot of difference between the most accurate measures of the chest rate strap and the EKG. So some of these devices or watches that measured heart rate from the wrist were way above and some were way below.

Now like I said before, Garmin wasn't included in this, but I've actually been pilot testing my Garmin, taking the heart rate measurements from the wrist the last few days while also wearing a chest rate strap.

And I found out that the Garmin is actually pretty far off, too, about 20 beats-per-minute over of what my heart rate usually is when measuring with the chest rate strap.

So, big significance, and if you rely on heart rate training I'm gonna say right now that you don't want to rely on a device that measures from your wrist, because how this works is basically there's a light underneath the face of this watch here that shoots light into your veins that reflects back and it basically measures how much blood is being pushed through that vein with each beat of the heart.

But there's so much variance based on the amount of ambient light and the movement, and that's really why you can't get an accurate measurement.

Why You Should Use A Heart Rate Chest Strap with your smart watch

Now, in defense of, you know, the Fitbit, the Apple, and the Mio, they're not saying that, you know, their wrist technology for measuring heart rate is the end-all be-all, and to be fair to them all, they all offer a heart rate chest strap that can pair up with your watch.

So if you're really into heart rate training, I think it's definitely worth investing in the chest strap so you're getting an accurate measurement.

So, that's the low-down on devices that measure heart rate from your wrist. Now if you want a really in-depth look at the pros and cons of heart rate training, head over to the Endurelite blog at where I have about a 10-minute video again explaining the pros and cons of heart rate training.