Apple Watch Series 12 and Ultra 4: Health Tracking Gets a Major Boost

Apple unveils its new smartwatches, the Series 12 and Ultra 4, featuring a redesigned health sensor system. Heart rate and heart rate variability (HRV) measurements are now 24 times more frequent, while workout mode battery life reaches 10 hours for the Series 12 and 45 hours for the Ultra 4.

A redesigned health sensor for more precise data

The new Health Sensing System relies on three hardware improvements: larger electrodes for better skin contact during ECGs, circularly arranged photodiodes for more efficient light capture, and larger, more energy-efficient green LEDs. As a result, heart rate is measured every 5 seconds — 60 times more often than before. Heart rate variability (HRV), a key indicator of the body’s ability to adapt to stress or exertion, is now sampled up to 24 times more frequently.

Users can switch between “day vitals” and “night vitals” views to detect changes in their metrics earlier. A new watch face complication also displays real-time step count, thanks to a revamped pedometer and AI algorithms for improved accuracy, especially indoors.

Software features focused on audio and AI

Both watches include improved microphones and the new S11 processor, enabling four Audio Intelligence features:

Sound Recognition: alerts the user to critical sounds (sirens, alarms, baby cries) via onboard intelligence, designed for those with hearing impairments.
Live Rewind: a double-press on the Digital Crown displays the last 15 seconds of a conversation as text, with the option to save or analyze it via Siri.
Siri Recap: automatically generates conversation summaries (title and key points) in the Siri app, with no audio recordings stored.
Shazam: song identification directly from the watch.

These features leverage Apple Intelligence and will be available with watchOS 27, set to roll out on September 14, 2026. The update will also cover some older models.

Battery, pricing, and availability

Battery life improves: the Series 12 lasts up to 10 hours in outdoor workout mode (+25% over the previous generation), with 15 minutes of charging adding up to 12 extra hours. The Ultra 4 goes further: 50 hours in daily use, 84 hours in power-saving mode, and a new Max Extended Workout mode for 45 hours of outdoor tracking. 15 minutes of charging adds 18 hours of battery life.

Pre-orders have been open since September 9, 2026. The Series 12 (42 mm and 46 mm) starts at $399, the Ultra 4 at $799. Deliveries begin on September 18.

New health metrics and iOS integration

Apple introduces a Readiness score, calculated from recent activity, training load, vitals, and sleep score. This real-time score helps assess one’s ability to tackle the day. A new Health Age feature will allow users, via the Health app on iOS, to compare their metrics (VO2 max, sleep, etc.) to their biological age.

The Health app will also offer movement assessments (flexibility, strength, balance) using vision-based AI models on iPhone and data from the Apple Watch. Users can also book and purchase blood tests (over 50 biomarkers) for $119 at roughly 2,000 Quest Diagnostics centers in the US.

“Overnight vitals now includes recovery HRV measurements analyzed against a user’s personal baseline, providing a more complete view of their health status.” — Apple, press releaseTranslated from French

With these watches, Apple is betting on precise health data and seamless AI integration, without overhauling the design. The improved sensors and new audio features could redefine daily smartwatch use, especially for athletes and health-conscious users.