Did you get a Fitbit for Christmas? If so, you might now be wishing you had held on to the receipt.
Earlier this week, the maker of the fitness tracker premiered a smartwatch, the Blaze. Shortly after, the company’s shares tumbled, ending the day down 18 percent, Time magazine reports.
And now Fitbit is facing a class action lawsuit alleging that its heart rate monitoring technology— which it calls PurePulse—is inaccurate, an issue first reported by The Verge.
That technology is found in its Charge HR and Surge devices, as well as the newly announced Blaze.
Essentially, Fitbit uses LED lights to monitor blood flow through a user’s wrist and, by using algorithms, can determine a user’s heart rate. Similar technology is used in the Apple Watch, along with several more competing smartwatches and fitness trackers.
According to the lawsuit, three different plaintiffs said they bought Fitbit devices based off the company’s advertised promise that it accurately tracked heart rates, according to Time.
Fitbit advertises slogans such as “every beat counts” and “know your heart”.
According to documents in the lawsuit, one plaintiff had a trainer manually count her heart rate during a workout. Her trainer recorded a heart rate of 160 beats per minute (bpm) while her Fitbit Charge HR indicated her heart rate was only 82 bpm.
Two other plaintiffs are mentioned in the suit, each citing similar experiences.
Time reports the lawsuit goes on to say that a cardiologist found Fitbit’s heart rate sensor consistently reported inaccurate results. With a heart rate of 110 bpm or higher, the lawsuit states the Fitbit devices often failed to record a heart rate at all. When a heart rate was recorded, the reading was off by an average of 24.34 bpm, the suit said.
Fitbit provided the following comment when contacted by Fortune magazine:
"We do not believe this case has merit. Fitbit stands behind our heart rate technology and strongly disagrees with the statements made in the complaint and plans to vigorously defend the lawsuit. Fitbit is committed to making the best clip and wrist-based activity trackers on the market. Our team has performed and continues to perform internal studies to validate our products’ performance.
"PurePulse provides better overall heart rate tracking than cardio machines at the gym, as it tracks your heart rate continuously – even while you’re not at the gym or working out. But it’s also important to note that Fitbit trackers are designed to provide meaningful data to our users to help them reach their health and fitness goals, and are not intended to be scientific or medical devices."
Fitbit’s shares were down nearly 6 percent in mid-day trading to US$22.86.