A new study claims Fitbit's fitness trackers don't accurately measure user's heart rate. That shouldn't come as a big surprise considering Fitbit's products don't undergo FDA approval, but the study itself is dubious first because of its questionable methods and second because it was commissioned by a law firm that's currently suing Fitbit.
According to the study, the Fitbit Surge and Charge HR don't accurately measure heart rate, and they get increasingly less accurate during moderate and intense workouts—precisely when you're most likely to want precise readings. The study goes on to say it may be the software algorithms Fitbit uses that skew readings. That's speculation on the study's part because analyzing Fitbit's code wasn't a part of the study.
That sounds pretty bad for Fitbit's products, but may not be as bleak as the study implies. The study included only 43 participants, and used a consumer-level electrocardiogram—a device that may not offer any better accuracy than the Fitbits it was measured against. Before the study can have any real meaning, a significantly larger number of participants need to be logged, and need to be monitored in a proper clinical setting with trained professionals using medical-grade electrocardiogram equipment.
Fitbit said as much in a public response to the study:
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.
That sums up the study's problems nicely and brings us to the big issue. The study was commissioned by the law firm of Lieff, Cabraser, Heimann, and Bernstein, which has a very vested interest in the outcome of the study since it's representing plaintiffs in a case against Fitbit and the heart rate tracking feature in its products. The results in the study can't be considered non-biased because of the way it was conducted and who it was conducted for. For Lieff Cabraser to get any value from the study, the results needed to reflect poorly on Fitbit, which they do.
The results don't look good for professional athletes who need accurate heart rate measurements, or people who need to closely monitor their heart rate for medical reasons. To be fair, those aren't the target market for general use wrist top fitness trackers; those people are looking to products like Mio's Alpha 2 heart rate tracker and other devices that focus on accurate heart rate tracking, or are using more precise electrocardiogram equipment.
All Lieff Cabraser has done is show that general use fitness trackers don't offer medical-grade heart rate tracking—something that's no surprise to anyone who's serious about fitness and health logging. In the end, their study did a poor job of showing what we already knew.
[Thanks to The Register for the heads up]