When the Apple Watch first came out, users were able to monitor their heart rate every 10 minutes throughout the day. Then there were “glitches,” or so the users thought, and the smartwatch became inconsistent with its heart rate readings. Apple updated their site today (brought to our attention by 9to5Mac), and it turns out the Apple bug was on purpose: the watch will no longer take your heart rate while your arm is moving. Apple hasn’t explained why they downgraded this feature, but some people guess that it’s to save on battery life.