The latest update to the Apple Watch left some users baffled, as the heart rate tracking is now irregular. According to Apple, however, it's all on purpose.

With the previous Apple Watch OS 1.0 software, the smartwatch recorded the wearer's heart rate every ten minutes, providing fairly accurate readings. With the latest Watch OS 1.0.1, meanwhile, users started complaining about irregular heart rate tracking, noting that the Apple Watch no longer measured their heart rate as frequently as it used to.

Users thought at first that it was some kind of bug that slipped into the new software and Apple would fix it with an upcoming update, but Cupertino has revealed that this change was in fact on purpose.

"You can check your heart rate any time using the Heart Rate Glance. And when you're using the Workout app, Apple Watch measures your heart rate continuously during the workout. This information, as well as other data it collects, helps Apple Watch estimate how many calories you've burned. In addition, Apple Watch attempts to measure your heart rate every 10 minutes, but won't record it when you're in motion or your arm is moving. Apple Watch stores all your heart rate measurements in the Health app," Apple explains on its updated support page.

The previous version of the software did not care whether you were in motion or were moving your arm, it still measured your heart rate every ten minutes. At the same time, some users said that the original Watch 1.0 software tracked their heart rate without any issues, but after the update the device is not as reliable anymore.

Apple has not commented on why it has chosen to alter the heart rate tracking functionality with its latest update, but some believe it may be an effort to extend battery life. Many Apple Watch users, however, would rather charge their device more frequently than have longer battery life at the expense of the heart rate sensor's accuracy. On the other hand, users did not see any change on battery life after the update, so Apple might have had another reason for changing the way its smartwatch tracks heart rate.