Lieff Cabraser Civil Justice Blog
Lieff Cabraser Announces That New University Study Finds Fitbit Charge 2 Can Underestimate Heart Rates by As Much As 30 BPM

Lieff Cabraser Announces That New University Study Finds Fitbit Charge 2 Can Underestimate Heart Rates by As Much As 30 BPM (UPDATED)

New Independent Study Confirms That Fitbit’s Heart Rate Monitors Are Highly Inaccurate

SAN FRANCISCO−A team of researchers from the University of Leeds (UK) and TSW xp LAB in Italy have published a new peer-reviewed study on the Fitbit Charge 2 fitness tracker that confirms findings in previous studies that the “PurePulse™” technology used in Fitbit’s popular fitness trackers can be extremely inaccurate during moderate and high-intensity exercise.

Participants in the new study were asked to ride a stationary bike “to raise their HR [heart rate] as much as possible.” The participants’ heart rates were then measured simultaneously by both a Fitbit Charge 2 and an electrocardiograph, the “gold standard” in heart rate monitoring. The results demonstrated that “the limits of agreement, which indicate the precision of individual measurements, between the Fitbit Charge 2 and criterion measure were wide (+16.8 to -28.5 bpm) indicating that an individual heart rate measure could plausibly be underestimated by almost 30 bpm.” In other words, as with “existing models of the same brand,” the Fitbit Charge 2’s “precision is poor.”

Moreover, as the study notes, previous tests have found that during cycling—the activity tested in this study—the Fitbit devices tracked heart rate more accurately than during other activities like “high HR walking and running.” So, while these results are very bad, if other exercise activities had been tested in this most recent study, the results could have been even worse.

These inaccuracies can put users at significant risk. As the authors explain, activity trackers are increasingly marketed and used to monitor serious health conditions, and “inaccurate measures of physical activity can affect the ability to monitor health status and are potentially dangerous for users.” “However accurate they may be at rest, the Fitbits are wildly inaccurate as heart rate monitors when worn during moderate- and high-intensity exercise, which is precisely the purpose for which Fitbit (in particular) markets them to consumers,” said Jonathan Selbin, one of the attorneys who filed a consumer protection lawsuit in 2016 on behalf of Fitbit owners who bought the devices to track their heart rates during exercise.

The new University of Leeds/TSW xp Lab study is the latest in an ever-increasing line of tests confirming the inaccuracy of Fitbit’s heart rate monitoring devices. The study’s authors note that “In the past 2 years, several studies have been published on the most recent predecessor of [the Fitbit Charge 2], the Charge HR. The large majority of these studies yielded similar results….”

Indeed, previous testing at the University of Wisconsin showed Fitbit tracker inaccuracies of between 20-40 beats, or 12.5-25%. In tests conducted at the Cleveland Clinic Heart and Vascular Institute, the Fitbit HR experienced a 16% error rate for heart rate during moderate treadmill exercise and “fell short” of the mark for consumers. A study at California State Polytechnic University, Pomona also found very significant inaccuracies in the Fitbit heart rate devices, and concluded that “at moderate to high exercise intensities, the average difference between the Fitbit devices and the ECG was approximately 20 beats per minute, well beyond any reasonable or expected margin of error.”

All this data corresponds closely with results of testing conducted in February 2016 by researchers at Ball State University in Indiana. They too found that the Fitbit heart rate devices were off by “20 or 30 beats per minute,” a margin of error they concluded was unacceptably high and “dangerous – especially for people at high risk of heart disease.” As that report put it, “The box for the Fitbit Charge HR says ‘every beat counts,’ but despite what the package says, the tracking device inside missed lots of them.”

These significant error rates stand in marked contrast to Fitbit’s extensive national marketing campaign, where the company claims the products will “count . . . every beat” and enable users to “know your heart.”

As the Fitbit devices are aggressively marketed to and for exercisers rather than those sitting quietly at rest, the performance deficiencies are a real problem, and Fitbit’s wearable trackers can provide flatly inaccurate information that can be dangerous to some users.

Although Fitbit has attempted to dismiss the studies with claims that the heart rate trackers are not “medical devices,” Selbin and others point out that Fitbit “claims to be a ‘Digital Healthcare Company’ and is actively trying to get corporations and insurers to make health care decisions based upon data they collect.” Fitbit knows its customers rely on the heart rate monitors to deliver accurate data, and promotes them for that very purpose in advertising and marketing. In an interview on CNBC, in fact, Fitbit CEO James Park touted Fitbit as not just a manufacturer of fitness trackers, but as a “digital healthcare company.”

Meanwhile, in an order issued in October 2016 in a different class action against Fitbit over alleged securities fraud arising from its sale of the Fitbit heart rate monitors, a San Francisco federal court cited three confidential witnesses from within Fitbit who state that the company knew about the inaccuracy of its heart rate monitors since at least 2014. According to the order, one of the confidential witnesses reported that Fitbit’s own internal studies found the “heart-rate monitoring devices to be highly inaccurate, particularly during vigorous exercise.”

Note: An earlier version of this release misidentified the study’s provenance. The relevant text has been updated to reflect that the study was the result of a collaboration between TSW xp LAB in Italy and the University of Leeds (UK).

Consumer Protection Attorneys at Lieff Cabraser

On January 5, 2016, attorneys at Lieff Cabraser, along with their co-counsel, filed a class action complaint on behalf of consumers seeking redress for Fitbit’s deceptive and misleading representations about its heart rate monitor products. The consumers claim that, as all the data demonstrates, Fitbit’s heart rate monitors cannot accurately or meaningfully record heart rates during high-intensity exercise, precisely what Fitbit advertised them for.

If you purchased a Fitbit heart rate monitor (Fitbit Charge HR, Blaze, and Surge), we invite you to visit our Fitbit heart rate monitor lawsuit page to contact a consumer attorney at Lieff Cabraser. We welcome the opportunity to learn of your experiences with your Fitbit heart rate monitor and to answer any questions you may have about your legal rights.

About Lieff Cabraser and Counsel

Recognized as “one of the nation’s premier plaintiffs’ firms” by The American Lawyer, Lieff Cabraser Heimann & Bernstein, LLP, has successfully litigated and settled hundreds of class action lawsuits in federal and state courts, including dozens of cases requiring manufacturers to remedy a defect, extend warranties, and refund to purchasers the cost of repairing the defective product. It has recovered billions of dollars for consumers in such cases. With seventy attorneys in offices in San Francisco, New York, and Nashville, we are among the largest law firms in the United States that represent only plaintiffs.

The consumer plaintiffs are also represented by Robert Klonoff and Levi & Korsinsky LLP.


Media Inquiries:
Lieff Cabraser Heimann & Bernstein, LLP
Jonathan D. Selbin, 212-355-9500