Skip to main content

Study finds inaccuracies in Fitbit's heart rate trackers, but questions remain

Fitbit will happily advertise the accuracy of its PurePulse heart rate technology in both the Charge HR and Surge, but are the readings accurate? It’s a question two researchers at the California State Polytechnic University tried to answer with their recent study, and the answer does not put Fitbit in a good light.

The study, which enlisted 22 male and 21 female healthy volunteers, sought to compare the heart rate readings of a time-synced electrocardiogram (ECG) to those from the Charge HR and Surge. Both wearables were placed on either participants’ wrists, while the ECG was done using a “previously validated and calibrated” heart rate measurement system, as well as a single channel ECG sensor and circuitry.

Recommended Videos

Participants were assigned to perform several indoor and outdoor tasks, including self-paced jogging, jump roping, treadmill running, stair climbing, and plyometrics, all of which were either followed or preceded by rests and all of which were performed for five minutes. In total, participants spent 65 minutes finishing their assigned tasks.

Unfortunately for Fitbit, results showed that the Charge HR recorded a heart rate that differed from the ECG’s data by 15.5 beats per minute (bpm). Meanwhile, the Surge recorded a heart rate that differed from the ECG’s results by an average of 22.8 bpm. The study also found that the Charge HR and Surge exhibited inconsistencies, with the devices showing a differential average of 10 bpm. However, the difference increased to 12.5 bpm when a participant’s heart rate reached 124 bpm, a heart rate associated with low intensity activities.

The study concluded that not only did the Charge HR and Surge record inaccurate heart rates when compared to an ECG, especially when participating in moderate to high-intensity exercise, but that their results even differed from each other. As such, the results have added fuel to the belief that Fitbit’s wearables don’t do a great job at measuring your heart rate, as well as the ongoing lawsuit that claims as much.

There are a few things to note about the study, the biggest of which being that it was commissioned by the lawsuit’s plaintiffs. As such, one can’t help but think this nugget of information slightly skews the results. In addition, the study doesn’t include as many participants as a study might want to have, which would help with the significance of the results.

Unsurprisingly, the company took issue with the study, calling it “biased, baseless, and nothing more than an attempt to extract a payout from Fitbit.” It also brought up Consumer Reports’ retesting of the Charge HR and Surge back in January, with the retest concluding that heart rates measured by both devices were accurate, regardless of the exercise’s intensity. Finally, a source familiar with Fitbit’s background told Gizmodo that the Zephyr BioHarness, the ECG that measured the participants’ heart rate, has “no validation that it’s any more accurate than our product.”

Even so, a 2014 article in the Berkeley Science Review and a February 2016 informal investigation by Indiana news station WTHR also arrived to similar inconsistent results with Fitbit’s trackers, with inconsistencies only increasing as the exercise grew in intensity.

In other words, we do not think the lawsuit against Fitbit will go away soon.

Williams Pelegrin
Williams is an avid New York Yankees fan, speaks Spanish, resides in Colorado, and has an affinity for Frosted Flakes. Send…
Digital Trends’ Top Tech of CES 2023 Awards
Best of CES 2023 Awards Our Top Tech from the Show Feature

Let there be no doubt: CES isn’t just alive in 2023; it’s thriving. Take one glance at the taxi gridlock outside the Las Vegas Convention Center and it’s evident that two quiet COVID years didn’t kill the world’s desire for an overcrowded in-person tech extravaganza -- they just built up a ravenous demand.

From VR to AI, eVTOLs and QD-OLED, the acronyms were flying and fresh technologies populated every corner of the show floor, and even the parking lot. So naturally, we poked, prodded, and tried on everything we could. They weren’t all revolutionary. But they didn’t have to be. We’ve watched enough waves of “game-changing” technologies that never quite arrive to know that sometimes it’s the little tweaks that really count.

Read more
Digital Trends’ Tech For Change CES 2023 Awards
Digital Trends CES 2023 Tech For Change Award Winners Feature

CES is more than just a neon-drenched show-and-tell session for the world’s biggest tech manufacturers. More and more, it’s also a place where companies showcase innovations that could truly make the world a better place — and at CES 2023, this type of tech was on full display. We saw everything from accessibility-minded PS5 controllers to pedal-powered smart desks. But of all the amazing innovations on display this year, these three impressed us the most:

Samsung's Relumino Mode
Across the globe, roughly 300 million people suffer from moderate to severe vision loss, and generally speaking, most TVs don’t take that into account. So in an effort to make television more accessible and enjoyable for those millions of people suffering from impaired vision, Samsung is adding a new picture mode to many of its new TVs.
[CES 2023] Relumino Mode: Innovation for every need | Samsung
Relumino Mode, as it’s called, works by adding a bunch of different visual filters to the picture simultaneously. Outlines of people and objects on screen are highlighted, the contrast and brightness of the overall picture are cranked up, and extra sharpness is applied to everything. The resulting video would likely look strange to people with normal vision, but for folks with low vision, it should look clearer and closer to "normal" than it otherwise would.
Excitingly, since Relumino Mode is ultimately just a clever software trick, this technology could theoretically be pushed out via a software update and installed on millions of existing Samsung TVs -- not just new and recently purchased ones.

Read more
How does Garmin measure stress, and is it really accurate?
Garmin Vivomove Sport dial close up. Credits: Garmin official.

Garmin watches are known for their robust activity tracking, but that's not all these fitness watches can do. Over the years, the company has been adding wellness features to its lineup of watches. These new health-focused metrics allow people to analyze their fitness and identify outside factors affecting their performance. One such factor is stress, which is something Garmin watches actively measures.
But you may be wondering—exactly how does Garmin measure stress? In this article, we break down how Garmin measures stress and delve into the accuracy of this metric. Should you trust your stress score? Read on to find out.

Is Garmin's stress score accurate?

Read more