Fitness Trackers May Be Giving You False Heart Rate Data


If you like to track your heart rate during exercise, you should think twice about the accuracy of your reading if you wear a popular “wrist-worn” device.

A study shows they could be wrong.

That’s what researchers at the Cleveland Clinic’s Heart and Vascular Institute discovered when they assessed how well four popular devices could track a person’s heart rate.

Ultimately, the researchers found that devices worn around the wrist proved far less accurate at providing a correct heart rate reading than traditional measuring devices, such as an electrocardiogram (EKG) or other trackers attached to the chest.

“These sorts of monitors are more of a consumer-driven device,” said lead author Dr. Marc Gillinov in a statement. “In the hospital, of course, we’re not going to rely on a wrist-worn monitor — and especially now that we know that they are not as accurate as an EKG.”

Study finds aberrations among leading brands

The Cleveland Clinic researchers looked at four popular wrist-worn devices – FitbitApple WatchMio Alpha and Basis Peak – and assessed how accurate those devices were during moderate and strenuous exercise when compared to an EKG.

For the study, researchers had 50 healthy adults run on a treadmill at speeds of up to six miles per hour with the popular fitness devices around their wrist. They assessed the devices’ heart-rate readings in comparison to the more traditional EKG reading.

The study found that, while the devices monitored a person’s heart rate accurately while at rest, the numbers skewed significantly as the study participants engaged in more strenuous exercise, according to the findings appearing in JAMA Cardiology.

“We found variable accuracy among the wrist-worn [heart rate] monitors,” states the study. “None achieved the accuracy of a chest strap-based monitor.”

Overall, Apple Watch and Mio Fuse devices returned the most accurate readings, while Fitbit and Basis Peak devices had a larger deviation.

“Assessment of the monitors’ accuracy is important for individuals who use them to guide their physical activity and for physicians to whom these individuals report [heart rate] readings,” the researchers wrote in the JAMA article.

Concern for cardio patients

Many patients being treated for cardiovascular or heart disease wear a fitness device to monitor their heart rate during exercise and stay within the boundaries suggested by a physician, notes a related story from the Cleveland Clinic.

“The wrist-worn fitness devices that include heart rate monitors are incredibly popular,” said Gillinov. “Patients come in and say, ‘My heart rate was 170,’ and want to know, is that true? Are these devices accurate? Now we can answer that.”

If you see an unusual spike in your heart rate reading, don’t panic. You may want to check again.

“Don’t make too much of a single reading, or even two readings,” said Gillinov. “Do several readings because you can’t count on these devices to be accurate every time.”

If you’re seeking more accurate heart-rate readings, you may want to use an alternative device, suggested Gillinov.

“If you really want to know your heart rate, wear the chest strap heart monitor because that senses electricity,” he said.