Is Your Fitbit Flawed?

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When the Fitbit launched a few years back, it seemed like the ultimate get-healthy solution. A tiny device that could track things like heartbeat, sleep, weight and food? A total no-brainer for the tech age.

But a recent study conducted by researchers at California State Polytechnic University, Pomona is showing that we might want to rethink the level of trust we have in the device. The unsettling thing the researchers found: The heart rate monitors on two Fitbit models (the Surge and Charge HR, in particular) can be off to the tune of up to 20 beats per minute. In addition, there were inconsistencies in heart rate when comparing the two devices—and in some cases, the devices didn’t record heart beat at all.

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“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,” the study—which was commissioned by Lieff Cabraser, the legal firm that’s behind the class action suit that is taking aim at inaccurate Fitbit readings—reported.

“Basically a Fitbit is shooting an LED into the skin of your wrist and looking for changes in blood flow. It uses this info to give you an idea of what your heart rate is at that moment,” explains Miraval exercise physiologist Andrew Wolf.

“In the study in question, they were comparing this to a machine that actually measures the electrical impulses created by the heart, which trigger a contraction. There is no way that a pulse meter on the wrist is going to be as good as an EKG, but you can do some simple things to get the best out of your wrist-based heart rate monitor. Remember that your Fitbit is actually trying to shoot light into your skin, so the thing has to be on tight. If you have bony wrists like me, you may even have to move the contraption up your arm a little bit in order to make sure you have good skin contact.”

“This is why I always use chest straps,” Wolf adds. “You can put them on and forget them because they are directly measuring electrical impulses from the heart and not blood flow away from the heart. The new Bluetooth models that make your phone into a heart rate monitor are even cooler.”

Since the study results were released, Fitbit has issued a response:

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. 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.

“Fitbit’s research team 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 Charge HR is the #1 selling fitness tracker on the market, and is embraced by millions of consumers around the globe.”

A lawyer from Lieff Cabraser tells NewBeauty that accuracy was taken into account in the study. “During the pilot (pre-experiment) tests, the professors performed concurrent Bioharness ECG and 12 lead ECG testing on 6 subjects to ensure similar readings were present—that is, to test the accuracy.”

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