Apple Watch Series 12: new health system checks your heart rate every 5 seconds

The Apple Watch Series 12 comes with a completely new Health Sensing System, using optical and electrical heart sensors that measure your heart rate every five seconds throughout the day. Heart rate variability is measured up to 24 times more often than before, split into a Recovery HRV and an overall HRV reading.

Also new is the Readiness Score: a daily 0-to-10 rating based on activity, recovery, and sleep, paired with concrete guidance (Recover, Pace Yourself, Ready, or Go For It). The watch also gains Audio Intelligence: it can recognize important sounds like a doorbell, rewind the last 15 seconds of a conversation for transcription, and automatically summarize it through Siri.

Battery life during an outdoor workout goes up to 10 hours (25 percent longer than before), and 15 minutes of charging adds 12 hours of battery. The Apple Watch Series 12 starts at $399, pre-orders are open today, and it hits stores on September 18.