Can You Trust Your Fitbit's Heart Rate?

Can You Trust Fitbit's Heart Rate Monitors?

New research shows that Fitbit devices have disturbingly inaccurate heart rate monitors, but the leader in fitness tracker devices says that the study is biased.

Researchers from California State Polytechnic University, Pomona, compared the heart rates of 43 adults wearing both a Fitbit as well as a bioharness connected to an electrocardiogram machine. They found that the Fitbit Surge and the Charge HR could be as off by as much as 20 bpm.

The study was commissioned by Lieff, Carbraser, Heimann, and Bernstein, the law firm behind a class-action suit against Fitbit that alleges that the heart rate monitors in the Charge HR, Surge, and Blaze are inaccurate, and could pose a health hazard for those who rely on it for precise heart rate measurements.

The Fitbit Charge HR and Surge were tested on 21 women and 22 men, who wore the device while resting (seated and standing), jogging on a treadmill, jumping rope, and climbing stairs. Researchers found that the Fitbits became less accurate during more strenuous activities.

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Update (5/23/16, 2:02 pm) Fitbit, in response, sent us this comment:

“What the plaintiffs’ attorneys call a “study” is biased, baseless, and nothing more than an attempt to extract a payout from Fitbit. It lacks scientific rigor and is the product of flawed methodology. It was paid for by plaintiffs’ lawyers who are suing Fitbit, and was conducted with a consumer-grade electrocardiogram – not a true clinical device, as implied by the plaintiffs’ lawyers. Furthermore, there is no evidence the device used in the purported “study” was tested for accuracy.

Fitbit’s research team rigorously researched and developed the PurePulse technology for three years prior to introducing it to market and continues to conduct extensive internal studies to test the features of our products. Fitbit Charge HR is the #1 selling fitness tracker on the market, and is embraced by millions of consumers around the globe.

Consumer Reports independently tested the heart rate accuracy of the Charge HR and Surge after the initial lawsuit was filed in January and gave both products an “excellent” rating. We stand behind our heart-rate monitoring technology and all our products, and continue to believe the plaintiffs’ allegations do not have any merit. We are vigorously defending against these claims, and will resist any attempts by the plaintiffs’ lawyers to leverage a settlement with misleading tactics and false claims of scientific evidence.”

For our part, we've found the Fitbit Charge HR to be as accurate as a chest strap heart rate monitor, and will continue our testing to further verify these results.

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