Merits of Plaintiffs'Fitbit Study Disputed

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By Julie A. Steinberg

May 26 — Fitbit disputes the merits of a recent plaintiff-commissioned study that a proposed class of consumers says supports its claims that the fitness trackers don't accurately measure heart rate ( McLellan v. Fitbit, Inc., N.D. Cal., No. 16-00036, amended complaint 5/19/16 ).

Kate McClellan and others sued Fitbit, Inc. in January in the U.S. District Court for the Northern District of California, alleging the company's ads are deceptive.

The Fitbit owners amended their complaint May 19 and cited new test results by Brett Dolezal, Ph.D. and Edward Jo, Ph.D. of California State Polytechnic University, Pomona.

The researchers conducted “the most comprehensive study to date,” and found that Fitbit’s PurePulse Trackers are inaccurate by an average of approximately 20 beats per minute during moderate to high intensity exercise, the new pleading says.

Fitbit Criticizes Study

Fitbit finds fault with the methodology and the conclusion of the study.

The company told Bloomberg BNA May 26 the study was poorly conducted and contains both data collection and basic math errors. Fitbit also said the new study doesn't demonstrate any shortcomings with Fitbit’s HR monitoring.

The company also maintains, as it previously has, that the Fitbit purchasers agreed to terms of service for their products that include mandatory arbitration clauses.

These provisions preclude the consumers from pursuing the suit in court, the company said.

Plaintiffs, meanwhile, continue to argue their suit should be heard in court, and not arbitrated, because of the company's fraudulent sales practices (17 CLASS 469, 5/13/16).

New Study, New Complaint

The new study’s proposed purpose was to compare heart rate measures and validate them against a criterion measure, a time-synchronized electrocardiogram (ECG).

The two academic kinesiologists tested 43 men and women for 65 minutes each, performing activities including jogging, jumping rope and climbing stairs—activities depicted by Fitbit when marketing the devices.

Each subject wore a Charge HR fitbit and a Surge Fitbit on different wrists.

The two Fitbit models tested include the heart rate function, called PurePulse tracking. The readings were measured against an ECG.

Kevin Budner of Lieff Cabraser in San Francisco told Bloomberg BNA May 25 the firm commissioned the study to further test the plaintiffs' allegations.

“We went for an honest appraisal that supported the hundreds of complaints” the firm got from dissatisfied Fitbit consumers.

Hired Guns?

But Fitbit said in a statement the study amounts to “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,” the company said.

Budner, however, told Bloomberg BNA, “These witnesses are not hired guns.”

The fact that plaintiffs’ lawyers paid for the study “is true but meaningless,” Budner said.

“It was designed and conducted by two leading academic kinesiologists at Cal Poly Pomona who, as the study itself discloses, specialize in this type of testing and have performed it many times before on similar products (and in fact validated those products in some instances),” Budner said.

“The notion that they would somehow design a faulty study or alter results and thereby put their academic reputation in jeopardy is absurd,” he said.

Further, “Fitbit’s claims that the ECG used as the reference was inadequate makes no sense,” Budner said. The device used in the study is not an “off-the-shelf ‘consumer' device” and is FDA-approved for ECG detection and transmission, he said.

Rigorous Research

Fitbit's statement also said it “rigorously researched and developed 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 told Bloomberg BNA May 26 the company's own studies support the validity of its wearables, but said it couldn't elaborate, citing the pending litigation.

The company statement also said Consumer Reports independently tested the heart rate accuracy of the Charge HR and Surge after the suit was filed against it 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,” Fitbit said.

Budner, however, said the Consumer Reports study only involved two participants on a treadmill.

“The juxtaposition of the Consumer Reports study and the academics' study couldn't be more stark,” he told Bloomberg BNA.

Study Findings

The plaintiffs' study found that, during moderate to high intensity exercise, the Charge HR recorded a heart rate that differed from the ECG by an average of 15.5 bpm.

The Surge recorded a heart rate that differed from the ECG by an average of 22.8 bpm.

“The report also confirms that the devices are not only inaccurate, but also surprisingly inconsistent,” the amended complaint alleges.

“The two devices simultaneously recording the same users' heart rate were off even from each other by an average of 10 bpm.”

The report concludes, “The PurePulse Trackers do not accurately measure a user’s heart rate, particularly during moderate to high intensity exercise, and cannot be used to provide a meaningful estimate of a user’s heart rate,” plaintiffs say.

“This is precisely what Plaintiffs have alleged, ” the complaint says.

Lieff Cabraser Heimann & Bernstein, LLP represents the plaintiffs.

Morrison & Foerster represents Fitbit.

To contact the reporter on this story: Julie A. Steinberg in Washington at

To contact the editors responsible for this story: Steven Patrick at

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