Lieff Cabraser Civil Justice Blog
New Independent Study Confirms Inaccuracy of Fitbit Heart Rate Monitors

New Independent Study Confirms Inaccuracy of Fitbit Heart Rate Monitors

New Independent Study by World-Renowned Cleveland Clinic and Revelations by Confidential Internal Witnesses Confirm Inaccuracy of the PurePulse™ Heart Rate Monitors Made by Fitbit, a Self-Proclaimed “Digital Healthcare Company”

Researchers at the Cleveland Clinic Heart and Vascular Institute, the top-ranked heart hospital in the nation, announced the results of new independent testing on a range of wrist-worn heart rate monitors, confirming the findings in previous studies that the PurePulse™ technology used in Fitbit’s popular fitness trackers is wildly inaccurate during moderate and high-intensity exercise. Dr. Marc Gillinov, the Cleveland Clinic cardiac surgeon who led that testing, noted that “as people exercised, the accuracy [of the products] diminished” and concluded that the Fitbit devices “had suboptimal accuracy during moderate exercise.” Moreover, Dr. Gillinov noted that “as people moved, the study had readings that could be off by 30 and 40 bpm, so it’s not a small difference.”

That finding is consistent with all previous rigorous studies (discussed further below), including that performed by California State Polytechnic University, Pomona in May 2016 as part of a class action lawsuit pending against Fitbit over alleged fraud in selling its Charge HR, Charge 2, Surge, and Blaze activity trackers.

The Cleveland Clinic study tested four different wrist-worn monitors and observed that the Fitbit Charge HR and the Intel Basis Peak (which is no longer being manufactured), in particular, “fell short” of the mark. Specifically, according to the study, the “Fitbit Charge HR underestimated HR during more vigorous exercise.” In fact the Fitbit Charge HR showed a 16% error rate during moderate treadmill exercise. (The Apple Watch and the Mio Fuse, in contrast, matched the chest strap ECG about 91 percent of the time.)

Tech website The Verge, reporting on the new testing, noted that these inaccuracies “could be risky for people who might push themselves too hard, and frustrating for those who wonder why a short jog makes their heart rate skyrocket.” The Cleveland Clinic researchers share that concern, noting that “validation of these devices . . . is imperative” because people “rely on these monitors to stay within physician-recommended, safe HR thresholds during rehabilitation and exercise.”

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 a recent 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 a new order issued last week 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 cites 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.”

Those allegations, and the findings of the Cleveland Clinic study, are not the first to raise red flags about the accuracy of Fitbit’s devices. They corroborate the results of the Cal Poly Pomona study from earlier in 2016, which found very significant inaccuracies in the Fitbit heart rate devices. That study noted 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.” A separate study conducted by the same Cal Poly Pomona researchers—which was published in the peer-reviewed Journal of Science and Medicine—also concluded that Fitbit’s heart rate monitoring devices “failed to satisfy validity criteria and demonstrated a substantial decrease in accuracy during higher exercise intensities.”

The data from both Cal Poly Pomona studies also 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.”

As the Cleveland Clinic’s Dr. Gillinov notes, “If you’re an elite athlete and you’re using your heart rate to guide training, or you’re a cardiac patient who’s been given specific heart rate targets or ranges, [you should] use a chest strap”—because Fitbit’s heart rate monitors don’t do the job.

Fitbit claims to have conducted “extensive internal studies,” to validate its heart rate monitors but refused to release the results of those studies and conspicuously stopped short of claiming that they support its claims that the heart rate monitors are accurate. A plethora of rigorous and independent studies show that they are not.

If the confidential witnesses are correct, Fitbit has long known that its heart rate monitors do not work as promised and hid that fact from its customers and the public for years.

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. The consumers also claims that Fitbit fraudulently tried to shield itself from liability for these defective products by tricking consumers into agreeing to an arbitration agreement, which the consumers argue should not be enforced.

If you purchased a Fitbit heart rate monitor (Fitbit Charge HR, Charge 2, 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.

Contact for media inquiries:

Lieff Cabraser Heimann & Bernstein, LLP
Jonathan D. Selbin