Apple Introduces Apple Watch Ultra 4 With Health Sensing System and Readiness Score

Apple has refreshed its rugged smartwatch line with the Apple Watch Ultra 4. The important changes are not on the outside but underneath: the watch is built around the new Health Sensing System and the S11 chip, which handle far more frequent heart rate and heart rate variability readings and a daily score for how ready the body is to train. Battery life now stretches past two days, and several of the new features run on Apple Intelligence.

Rebuilt sensors and measurement accuracy

The optical and electrical heart sensors have been redesigned. Larger, power-efficient green LEDs let the watch read heart rate every five seconds throughout the day rather than only during workouts. Those continuous background readings also make the Move and Exercise rings more accurate, and current heart rate is available on a dedicated watch face complication.

Heart rate variability is now sampled up to 24 times more often, and the data is split into two separate metrics. Recovery HRV tracks daily signals of stress and recovery, while overall HRV is meant for a longer-term view of cardiovascular health. Overnight vitals now include recovery HRV measured against a personal baseline, and a new daytime view lets users compare day and night metrics side by side.

The pedometer has been rewritten as well, with new machine learning algorithms that, according to Apple, improve step counts and distance accuracy during indoor workouts. The company also claims the most accurate GPS among sports watches and the most accurate heart rate sensing among wearables. Both claims rest on Apple's own testing, including a study with more than 1,000 participants.

A daily readiness score

The headline software addition is readiness. The watch weighs recent activity, training load, vitals and sleep score, then returns a single number from 0 to 10 along with one of four recommendations: Recover, Pace Yourself, Ready or Go For It.

The score is recalculated during the day if the user completes an intense workout or daytime vitals shift, and the watch shows which factors are pushing the number up or down. The scoring algorithm was built on data from the Apple Heart and Movement Study together with exercise scientists and physicians at Apple.

Battery life and workout modes

In everyday use the Apple Watch Ultra 4 runs for up to 50 hours, comfortably more than two days, and up to 84 hours in Low Power Mode. Charging is quicker too: 15 minutes on the charger buys roughly 18 hours of use.

Long sessions are covered by two dedicated modes. Extended Workout tracks a session with full GPS and heart rate for up to 25 hours, a 25 percent improvement over the previous model. Max Extended Workout stretches tracking for runs, walks and hikes to 45 hours while still logging GPS coordinates every second. That is usually enough to finish a 100-mile race.

The redesigned Health app

Alongside the watch, Apple has rebuilt the Health app on iPhone. It gains an Insights tab that surfaces timely readings and a Longevity tab that analyses long-term data. The latter includes Health Age, which shows how selected metrics compare with the user's actual age.

The app also adds movement evaluations that assess flexibility, strength and balance using vision-based AI models on iPhone together with heart rate data from the watch. In the United States, users will be able to book lab panels covering more than 50 biomarkers for $119 at roughly 2,000 Quest Diagnostics locations. The update arrives later this year, starting in U.S. English.

Audio Intelligence and Siri on the wrist

A separate group of features combines the built-in microphone, the S11 chip and Apple Intelligence models. Audio Intelligence is meant to help users notice important sounds around them and recover what was said in a conversation.

Live Rewind shows a text snippet of the previous 15 seconds of a conversation after a double press of the Digital Crown, so a missed phrase can be read back.

Siri Recap produces a short summary of a conversation with a title and key points, saved in the new Siri app for later.

Sound Recognition alerts deaf and hard of hearing users to sirens, alarms, doorbells or a crying baby even when an iPhone is not nearby.

Apple stresses that no audio recordings are created or stored: sound is processed inside Secure Exclave, a hardware-isolated compartment in the S11 chip that deletes the data immediately after analysis. Each feature is opt-in, and Live Rewind plays a chime and shows a microphone indicator so people nearby can tell it is running. Live Rewind and Siri Recap arrive in beta later this year.

The software base is watchOS 27, which brings Siri AI powered by Apple Intelligence: the reworked assistant understands personal context and lets users continue conversations straight from the wrist. Other changes include a dynamic grid of five suggested apps, a one-handed tap gesture for picking widgets in the Smart Stack, perimenopause and menopause support in Cycle Tracking, and Workout Buddy working without an iPhone nearby.

Cases and bands

The case comes in natural and black titanium and is 3D printed from fully recycled titanium. The autumn band collection brings new colours: Trail Loop in dark umber, sand and burgundy, Alpine Loop in desert, dark olive and burgundy, and an Ocean Band made from translucent silicone for the first time.

Apple Watch Hermès Ultra 4 is offered separately in natural titanium. It adds a Grand H titanium band with a built-in extension mechanism for wearing the watch over a wet suit, plus the new Fathom and Wonder face with four views of the ocean's depths.

Specifications

• Processor: Apple S11 with Secure Exclave
• Sensors: Health Sensing System, new optical and electrical heart sensors, readings every 5 seconds
• Navigation: GPS with on-device route processing, per-second logging in Max Extended Workout
• Battery life: up to 50 hours in normal use, up to 84 hours in Low Power Mode
• Workout modes: Extended Workout up to 25 hours, Max Extended Workout up to 45 hours
• Charging: 15 minutes for around 18 hours of use
• Case: 3D-printed titanium, 100 percent recycled titanium
• Colour: natural titanium, black titanium
• Operating system: watchOS 27 with Apple Intelligence
• Health features: readiness score, overnight and daytime vitals, recovery HRV, ECG app, heart health notifications
• Safety: satellite communications, Emergency SOS