Fitbit’s PurePulse heart rate tracking might not be as accurate as the company promises them to be, and that makes the device dangerous. Researchers from California State Polytechnic University compared the firm’s heart rate monitors with the number recorded by an electrocardiogram (ECG) and reportedly found that the wearable devices read on average 9 beats per minute (bpm) less than users’ real heart rate.

The firm that spent three years developing its PurePulse technology is currently facing a fraud class-action lawsuit. Also, the Lief Cabrasser law firm commissioned the study to test out the efficiency of the product. It’s worth mentioning the firm was released in 2014 with the Charge HR wearable. 

Fitbit's activity wristband packing a lot of fitness features could also pack a compilation of inaccurate data
Fitbit’s activity wristband packing a lot of fitness features could also pack a compilation of inaccurate data, endangering its users. Image Credit: Wearable

The plaintiffs claim the PurePulse technology built in Fitbit wristbands failed to record accurate and consistent heart rates during the wearer’s moderate or intense physical activity. Which is the opposite to the consumers’ expectations based on the company’s marketing campaign.

The study shows that Fitbit gadget’s recorded numbers could be up to 23 bmp off compared to the readings of an ECG. The Lief Cabrasser law firm said that’s well beyond an acceptable margin of error, PC Magazine reported.

“The PurePulse technology embedded in the Fitbit optical sensors does not accurately record heart rate, and is particularly unreliable during moderate to high intensity exercise,” the study affirms.

A spokesman for Fitbit reacted by claiming the company extensively conducts internal studies that prove the accuracy of its heart rate monitoring wristbands, according to a report by The Telegraph.

The spokesman accused the researchers of carrying out a baseless study as part of an attempt to extract money from the company. He also questioned the reliability of what he says it is a consumer-grade electrocardiogram. FitBit’s spokesman noted there was no evidence that it was a true clinical device.

He also suggested the fact that the study was paid by plaintiffs’ lawyers gave a reason to doubt the effectivity of the methodology used, according to the statement. The firm is going to do what it takes to defend itself against the lawsuit, added FitBit’s spokesman.

The study and what its results represent

What tells Fitbit’s devices apart from competitors is that they have a PurePulse sensor. The ‘clinical’ device is able to detect blood volume changes in the wearer. The device relies on LEDs reflected on the user’s skin to notify them of any trouble. The Fitbit software’s calculations then result in the difference in the wearer’s heart rate.

he FitBit's 'medical' wristband has been questioned recently as a study shed light on its accuracy.
The FitBit’s ‘medical’ wristband has been questioned recently as a study shed light on its accuracy. Needless to say the wristband’s data surprised researchers, and not in a good way. Image Credit: Forbes

The products involved in the study were two Fitbit models designed to track wearers’ heart rates, steps walked, sleep quality and calories burned. The Surge and Charge HR, which cost $199 at Amazon, was tested on 43 healthy adults. The test consisted on tracking their physical activity across 65 minutes. Studying the participants while jogging, running, climbing stairs and jumping rope, gave researchers all they needed.

Meanwhile, they were connected to an ECG, which is designed to assess the heart’s muscular and electrical functions.

Researcher’s opinion on Heart Rate’s efficacy 

The researchers found the inaccuracy of Fitbit’s devices increased along with the level of activity. In fact, the average margin of error of 9 bpm jumped to nearly 17 bpm during exercise.

Moreover, the heart rate readings shown by the Charge HR and Surge were different to one another when tested on the same wearer.

The lawsuit against Fitbit states that, defects in its PurePulse models could lead to dangerous consequences. Because wearers could mistakenly decide to achieve risky heart rates by relying on a highly inaccurate heart rate readings, The Telegraph reported.

Source: The Telegraph