1. ITV Report

Fitbit accused of putting customers in danger with 'wildly inaccurate' heart rate readings

The Fitbit Charge HR. Credit: Fitbit

Fitness technology company Fitbit has been accused of putting customers in danger with "wildly inaccurate" readings from their heart rate trackers.

Fitbit sells products which claim to monitor users' heart rates, the number of calories they burn, steps they take and level of sleep quality.

But some users in the US are trying to sue the firm, saying the devices do not "do not and cannot consistently and accurately record wearers’ heart rates during the intense physical activity for which Fitbit expressly markets them".

They are now trying to sue the firm, which has strongly denied the allegations.

Here's everything we know.

  • What are the allegations?
A promotional picture from Fibit. Credit: Fitbit

The claimants say the devices pulse trackers "do not work, and their heart rate readings are wildly inaccurate".

The "significant" margins of error make the trackers "effectively worthless" and could lead to "dangerous heart rates", the lawsuit claims.

The defect...presents a safety hazard because Class members’ could jeopardise their health by relying on the inaccurate heart rate readings and potentially achieving dangerous heart rates.

– Lawsuit

Fitbit - which has promoted the products using slogans such as "Every Beat Counts" - is also accused of "defrauding the public and cheated its customers".

One claimant alleges that her personal trainer recorded her heart rate at 160 beats per minute but her Fitbit product only gave a reading of 82 bpm.

Another claimant - whose doctor had advised him not to exceed 160 bpm because of health problems - claims his device underestimated his heartrate by as much as 25 bpm.

One Twitter user, Nick Bailey, took to social media to question the readings from the Fitbit he purchased for his wife.

  • How are the trackers meant to work?

Fitbit products are said to use LEDs that reflect on to the skin to monitor changes in blood flow through a user's wrist.

Algorithms then turn this data into a heart rate measurement.

  • How have Fitbit responded?
Fitbit says it will 'vigorously defend the lawsuit'. Credit: Fitbit

The firm has vehemently denied the claims.

In a statement, it said:

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