The Apple Watch allegedly delivers inaccurate heart rate readings that do not track workouts such as P90X or CrossFit. Complaints to this effect have been posted on Apple's Support Communities forum as well as on Reddit.
According to Apple Insider, users started complaining about alleged inaccurate heart rate readings on the Apple Watch. Some users even reportedly got replacement watches from the company.
"I have been using my Apple Watch to track my workout sessions and for the past few days I have noted that whenever I am doing intense workouts where there is lot of hand movements like P90x3 or Insanity the Apple watch heart rate sensors gives wrong readings," an Apple Watch user said in a compliant posted on the company's community forum.
Some users even compared the heart rate monitoring of the Apple Watch with Polar's Heart Rate Monitor chest strap, and found it to be "grossly out of alignment". "I go back and forth between using my AWS and my Polar (with chest strap) during workouts. My Polar will read accurately, but my AWS will frequently read 60ish BPM while working out and I can clearly feel my heart rate elevated," another user wrote in a Reddit post.
The Apple Watch uses photoplethysmography process to calculate the heart rate by analysing blood flow. This appears to be the reason behind the inaccuracy. There are two photodiode sensors that work in tandem with infrared LEDs to monitor the flow of blood and to deliver results every 10 minutes.
Apple has not commented on any complaint but acknowledges the inaccuracy through a support page that reads: "Apple Watch may not be able to get a reliable heart rate reading every time for everybody." Some of the factors that can affect the performance of the Apple Watch include skin perfusion, motion and permanent or temporary changes to the skin. In addition, inaccuracy can be from the software side as the Apple Watch works with the company's proprietary Health app to store heart rate measurements.
Last week, the company released its watchOS 2.0.1 for the Apple Watch that primarily resolved battery performance issues and fixed the bug that allows the built-in sensors "to stay on indefinitely" when using Siri to measure the heart rate.