Popular Wearable Heart Monitors May Be 'Highly Inaccurate'

(HealthDay News) — Fitbit heart rate trackers are "highly inaccurate," according to a new study commissioned by the law firm Lieff Cabraser, which is handling a class action suit targeting three Fitbit models that use the PurePulse heart monitor: Fitbit Blaze, Fitbit Charge HR, and Fitbit Surge.

The heart rates of 43 healthy adults were checked during rest and exercise using Fitbit's PurePulse heart rate monitors. Their heart rates were then checked with a BioHarness device that produced an electrocardiogram, CNBC reported. The results showed that the Fitbit monitors miscalculated heart rates by up to 20 beats a minute during more intensive exercise, the researchers at California State Polytechnic University in Pomona found.

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A Fitbit statement posted by Gizmodo challenged the findings: "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," according to the statement, CNBC reported. "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."

Earlier this year, a separate study by Ball State University in Indiana and NBC-affiliated TV station WTHR found that the Fitbit Charge HR had an average heart rate error rate of 14 percent, CNBC reported. "Calculating a heart rate that's off by 20 or 30 beats per minute can be dangerous -- especially for people at high risk of heart disease," that study authors warned. In a written reply to WTHR, Fitbit said its devices "are designed to provide meaningful data to our users to help them reach their health and fitness goals, and are not intended to be scientific or medical devices," CNBC reported.

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