Some Apple Watch users complain of irregular heart rate readings after more intense workouts

It might be time for a firmware update/bug fix for the Apple Watch.

A number of Apple Watch owners have reported inconsistent or inaccurate heart rate measurements while exercising, with some saying issues have continued even after receiving replacement watches from Apple, calling into question one of the wearable’s signature features.

The issue, which Apple has yet to classify or acknowledge as a widespread problem, seems to result while trying to monitor high-impact exercises. A thread on Apple’s Support Communities forum has received more than 3,000 views and 17 replies, and nearly a dozen threads on the issue have been started on reddit.

Exercise regimens, such as P90X or CrossFit, have resulted in complaints regarding heartbeat monitoring while less intense workouts seem to return more accurate results. For example, one user on reddit says his Watch displays a resting heart rate in the range of 60 to 80 beats per minute during strenuous sessions which should register above 140 bpm.

The Apple Watch calculates a user’s heart rate by analyzing blood flow in the wrist using a process called photoplethysmography. This approach has limitations, as discovered at launch time when users’ with tattoos on their wrists reported being unable to use the device as advertised.

Apple’s web site acknowledges that different types of motions can also affect the heart rate readings, making rhythmic motions such as running or cycling more accurate than “irregular movements,” such as tennis or boxing — which could include interval training programs mentioned in user complaints.

Stay tuned for additional details as they become available and if you’ve seen this issue on your end, please let us know in the comments.

Via AppleInsider, Apple discussions forum and Reddit