Fitbit's wristbands don't accurately measure heart rates and fail to provide a "meaningful estimate" of beats per minute (bpm), a study has claimed.
Researchers from California State Polytechnic University say the PurePulse technology, that tracks a person's heart rate in Fitbit's wearables, is "inaccurate" and "inconsistent". "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," Edward Jo and Brett Dolezal from the university, say in a paper.
Fitbit has been facing a lawsuit over the accuracy of its devices since January and the study was commissioned by the lawyers representing those who are against the company. A spokesperson for Fitbit told CNN the study "lacks scientific rigour and is the product of flawed methodology".
Fitbit said the research "was paid for by plaintiffs' lawyers who are suing Fitbit, and was conducted with a consumer-grade electrocardiogram (ECG) – 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."
The two researchers tested the Fitbit Charge HR and the Fitbit Surge monitors on 22 men and 21 women living in Los Angeles. One of each trackers was fitted on each wrist of the participants and those wearing the devices completed a number of exercises, including jogging, skipping, and climbing stairs.
To provide a comparison for the results the researchers also monitored heart rates with a EGC.
The results from both devices showed a difference in heart rates to the ECG. The Surge was an average of 22.8 bpm off of the ECG, while the Charge HR recorded a difference of 15.5 bpm.
The findings, which are based on more than 40 hours of recorded data, showed heart rate varied from the ECG more when the intensity of the exercise increased. The results also varied between each fitness tracker. "Disruptions to continuous heart rate detection in both Fitbit devices were quite common during testing periods based on manually recorded data," the researchers said. They continued to say that they suspect the algorithms powering the heart rate system "lack proper sophistication".
It isn't the first time that allegations have been made against the accuracy of the data recorded by Fitbit devices.
In January 2016, a class-action lawsuit was issued against the company over the Fitbit Blaze and both of the wearables tested by the researchers. At the time the lawsuit said that the devices were "falsely representing" what they could measure and demanded the company offer customers a refund.
Following the publication of the new study the lawyers representing those complaining about the quality of the devices filed an amended lawsuit. "These devices simply are not accurate at measuring heart rates during moderate or high intensity exercise," said attorney Jonathan Selbin from Lieff Cabraser in a statement.
WIRED contacted Fitbit for further comment but nobody was available at the time of publication.
This article was originally published by WIRED UK
