A Class-Action Suit Claims Fitbit Devices Inaccurately Measure Heart Rate

Fitbit’s wristbands don’t give accurate heart rate readings during intense exercise, dissatisfied customers allege.

A Class-Action Suit Claims Fitbit Devices Inaccurately Measure Heart Rate
[Photo: Flickr user Kārlis Dambrāns]

A group of Fitbit customers filed a class-action suit against the company Tuesday, alleging the Fitbit Charge HR and Surge fitness-tracking wristbands don’t accurately measure heart rates during exercise.


“Fitbit marketed these products through aggressive and widespread advertising to consumers who were not only deceived in the devices’ true functionality, but who also were put at a safety risk by trusting the Fitbit Heart Rate Monitors’ inaccurate measurements,” Robert Klonoff, one of the customers’ lawyers, said in a statement. “Many thousands of consumers paid a premium to get accurate heart rate monitors, and instead got devices that do not work as promised.”

According to a complaint filed in California federal court, a cardiologist compared the wristbands’ readings to a standard electrocardiogram, and found a “significant degree” of variation.

“At intensities over 110 [beats per minute], the Heart Rate Trackers often failed to record any heart rate at all,” according to the complaint. “And even when they did record heart rates, the Heart Rate Trackers were inaccurate by an average of 24.34 bpm, with some readings off by as much as 75 bpm.”

In an email to Fast Company, a Fitbit spokeswoman says the company “strongly disagrees with the statements made in the complaint and plans to vigorously defend the lawsuit.” Fitbit says its wristbands provide “better overall heart rate tracking than cardio machines at the gym, as it tracks your heart rate continuously even while you’re not at the gym or working out” and aren’t intended to be scientific or medical devices.

The company’s terms of service require that disputes be resolved through arbitration, but the customers say those contract clauses are hidden in Fitbit’s terms of service and not disclosed to customers who buy the wristbands from third-party merchants.

“They are brought to the attention of consumers who purchased at third-party websites and retail locations only after they buy their Fitbits and visit Fitbit’s website to register them,” lawyer Jonathan D. Selbin, also representing the Fitbit customers, said in a statement. “Fitbit recently admitted in court documents in an unrelated case that the Fitbit devices cannot function properly without registering them on Fitbit’s website. And just by visiting that website, Fitbit purports to bind you to the arbitration clause and class action ban.”


The customers are seeking actual and punitive damages on behalf of customers who bought the devices through third-party merchants and didn’t sign on to the arbitration terms.

The same PurePulse-branded heart rate tracking is used in Fitbit’s new Blaze smartwatch-like fitness tracker, according to the lawsuit. The Blaze was unveiled earlier this week to a mixed reception and a decline in Fitbit’s stock price, as analysts compared it unfavorably to the similar-looking Apple Watch.

About the author

Steven Melendez is an independent journalist living in New Orleans.