Product1 publisher2 min readPublished
An hour of walk-run intervals put the Series 12 within 1.9 bpm of a Polar chest strap
Apple says the Series 12 and Ultra 4 are the most accurate heart-tracking wearables on the market. One reviewer's hour of walk-run intervals, judged against the same chest strap Apple's own accuracy study used, mostly backs it.
The Product Desk · Product desk
What happened
- ZDNET wore an Apple Watch Series 12 on one wrist, a Pixel Watch 5 on the other and a Polar H10 chest strap through a run in Brooklyn's Prospect Park, alternating walking and running every ten minutes.
- Measured against the strap over that hour, the Series 12's mean absolute error was 1.9 bpm and the Pixel Watch 5's was 5.3 bpm.
- The reviewer traced the gap to the recovery transitions between intervals, where the Apple Watch came within a few beats per minute of the strap's peak and the Pixel Watch fell behind.
- The Polar H10 is the strap Apple used as the reference in its own recent Heart Rate Accuracy Study, according to ZDNET.
- The Series 12 reads heart rate every five seconds and HRV every five minutes, 60 times and 24 times as often as the Series 11's five-minute and two-hour intervals.
Compiled by The Product DeskSomething wrong?How this is made
Why it matters
- constraint Sensor precision stops mattering once the product's visible output is a workout recap or a weekly average, because both watches produced the same average on the same hour.
- capability Wrist-worn recovery and HRV scoring now has a defensible basis, at least for one wearer over one hour of intervals.
- decision A team choosing a validation reference can hold its own device to the H10 and be judged on the same instrument Apple picked for its accuracy study.
- precedent Apple's market-wide accuracy claim is being settled in public by single-reviewer comparisons against one rival, months before the software that consumes the data reaches users.
The one number both watches agreed on was the session average: 132 bpm on the strap, 132 on the Series 12, 132 on the Pixel Watch 5 [5]. A summary card that reports a workout average would have shown a user the same figure either way.
Reading by reading, correlation to the H10 came out at .998 for the Apple Watch and .943 for the Pixel Watch [7]. The gap in mean absolute error is 3.4 bpm [1]. Google's error is about 2.8 times Apple's [2]. Against that 132 bpm average, the two errors work out to roughly 1.4 percent and 4 percent [3].
ZDNET's reviewer located the difference in the recovery transitions, the stretch after each ten-minute run turned back into a walk [2]. "The Apple Watch paced closer to the chest strap, while the Pixel Watch lagged," the reviewer wrote [9].
ZDNET credits Apple's Health Sensing System, which it describes as using stronger sensors than previous generations to take more frequent heart rate and HRV readings [12]. The denser sampling is what makes the two HRV figures Apple now reports and the daytime Vitals feature possible, and it is meant to feed longevity features such as Health Age [13]. The Readiness score and the rest of the longevity set arrive later this year [14]. ZDNET declined to give a buying recommendation, citing the new Health app, Siri Recap and Live Rewind all landing later in the year, and one day of use with the Readiness score [15].
Whether 3.4 bpm matters to a product depends first on whether the feature uses averages or transitions. A weekly resting-rate chart or a workout recap sits on numbers both watches produce identically, so a user sees the same thing either way. A recovery score or an HRV trend depends on exactly the seconds where the two watches diverged. The other factor is timing. The five-second heart rate stream is on the wrist today [11]; the Apple software that turns it into a score is dated to later this year [14].
Apple's claim is market-wide. ZDNET reports Apple saying the Health Sensing System makes the Series 12 and Ultra 4 the most accurate heart-tracking wearable devices on the market [4]. The evidence here is one wearer over one hour, against a single competing watch. Oura, Whoop and Garmin, which ZDNET names among Apple's nearest competitors on trackable biometrics, were left out of the comparison [16].
What to watch
- Whether the 1.9 bpm result holds beyond one hour of clean intervals, across other wearers, workouts and skin tones.
- ZDNET's full review once the revamped Health app, Siri Recap and Live Rewind ship later this year.
- A comparison that includes Oura, Whoop or Garmin, the devices Apple's market-wide accuracy claim would have to beat.