Health tracking represents the biggest change for the Apple Watch Series 12. Apple has redesigned the sensor array on the back of the watch with a second-generation electrical heart sensor, photodiodes arranged in a ring, larger and more efficient green LEDs, and a larger electrode contact area for ECG readings. The practical result is that heart rate checks now occur every five seconds, whether you’re sitting at a desk, walking, or exercising, compared to about every five minutes on previous models while stationary. This represents a dramatic increase in data resolution.
Apple claims it’s the most accurate heart rate detection of any wearable device, citing a company-sponsored study of more than 1,000 participants. HRV tracking has also become more granular. Apple now divides it into Recovery HRV, which captures short-term stress and fatigue signals, and Global HRV, which provides longer-term cardiovascular context. The Vitals Experience adds a daytime view with finer classifications – including off, slightly off, typical, favorable – giving you a more nuanced picture of how your body reacts throughout the day. The sheer volume of data can reveal patterns you wouldn’t have noticed before.
Readiness Score is Apple’s most direct response to the recovery metrics offered by Oura Ring, Whoop, Fitbit, and Garmin. It combines activity, training load, sleep score, overnight vital signs, daytime heart rate and HRV data, as well as recent behavior, into a score from 0 to 10 across four levels. “Recover” is at the bottom, “Go For It” is at the top. Unlike most competitors, the score is updated throughout the day rather than locking in every morning: a nap or hard workout can change it. And unlike Oura, Apple provides the underlying factors and long-term trend data without a paid subscription, which is a significant differentiator.
One caveat to the Readiness Score: It requires at least seven nights with about four hours of sleep to establish a baseline, which means I only had a few days of usable data. The first readings seemed reasonable, but it’s best to treat them as a prompt to check how you actually feel, not as a definitive verdict on whether to continue with a workout.
Apple also claims that a redesigned ML-powered pedometer provides more accurate step counts and indoor walking and running distance, calling it the most accurate step tracker of any smartwatch. A new Steps complication on the watch face is a welcome addition: it’s useful to check a live countdown without opening an app. In practice, I didn’t notice any obvious improvement in step count accuracy after a week, although I’m also not someone who regularly pays close attention to my steps.
All existing health and safety functionalities are fully retained. ECG, blood oxygen (if available), sleep stages and scores, sleep apnea notifications, temperature detection, cycle tracking, fall detection, accident detection, emergency SOS, etc. are all present. Availability varies by region and regulatory authorization, and none of this replaces a professional medical diagnosis, although I can’t help but wonder when or if that might change. I’ve talked about this before, but some of the health tracking features of these types of wearable devices can be truly life-changing in medical scenarios. An Apple Watch was the first device to give me an indication that I might have atrial fibrillation – something I took to my cardiologist and which ultimately led to surgery.
