Consumer Reports is saying that the optical heart rate monitoring in Fitbit's Charge HR and Surge wrist trackers is actually "very accurate," based on some recent tests that the stalwart review publication conducted.
The tests follow a class-action suit filed against Fitbit earlier this month, in which plaintiffs from California, Colorado, and Wisconsin said that Fitbit's heart rate monitoring capabilities didn't work as advertised by the company, especially during intense exercise.
Fitbit responded at the time with a statement saying it "strongly disagrees with the statements made in the complaint" and that its proprietary heart rate-reading technology, called PurePulse, "provides better overall heart rate tracking than cardio machines at the gym." Fitbit has also pointed out that its wrist-trackers aren't meant to be scientific or medical devices.
Fitbit devices vs. a Polar chest strap
In the Consumer Reports test, two testers — a female and a male — wore Fitbit Surge and Fitbit Charge HR devices on their wrists and compared the wrist-based heart rate readings to the levels measured by Polar chest straps. (Chest-based heart rate monitors are widely recognized as more accurate devices for measuring heart rate during workouts, even as more and more tech companies try to fine-tune wrist sensors.) "During nearly every trial, the variance between the chest strap and the Fitbit devices amounted to no more than three heartbeats per minute," Consumer Reports writes.
Fitbit's newest product, the Blaze watch, also has optical heart rate sensors, but until that one actually ships later this year, we won't be able to say for sure how well it tracks heart rate. Fitbit has increased the sampling rate for that watch though, which doesn't necessarily mean the heart rate tracking will be more accurate than other devices, but it will be captured more frequently.