Apple’s new heart rate sensor in the Apple Watch Series 12 has just faced its first serious independent accuracy test, and it came surprisingly close to a dedicated chest strap. The watch was tested during indoor cycling, running, and weightlifting against the Polar H10 ECG chest strap, a device commonly used as a reference for heart rate testing.
According to a report from 9to5Mac, Rob ter Horst of The Quantified Scientist ran the comparison. The Series 12 produced results that were particularly close during indoor cycling, while also staying highly correlated with the Polar H10 during running and weightlifting.
The Series 12 Gets Surprisingly Close To A Chest Strap
The Series 12’s redesigned heart sensor measures heart rate every five seconds, including when the wearer is not exercising. Older Apple Watch models measure background heart rate at five-minute intervals.
That faster sampling is one thing. Seeing how closely those readings track a dedicated chest strap during actual workouts is another.
Indoor cycling produced the most striking result. The Series 12’s heart rate readings were almost identical to the Polar H10’s, with a correlation close to a perfect 1.0.
Running was not far behind, reaching a 0.98 correlation. The main differences appeared at higher heart rates. Weightlifting, which is particularly challenging for wrist-based heart rate sensors because of arm movement and changes in grip, reached 0.97.
Ter Horst described the weightlifting result as quite good and said it put the Series 12 above 85 percent of the wearables he has tested specifically for that activity.
The Series 11 Still Beat It During Running
There is an interesting twist to the results: the new Series 12 did not beat Apple’s previous generation in every test.
Ter Horst has tested the Apple Watch Series 11 extensively and found broadly similar heart rate accuracy between the two generations. During running specifically, however, the Series 11 performed slightly better.
That makes the comparison more interesting than a simple new-sensor-is-better story. The Series 12’s new hardware can closely track a dedicated chest strap, but that does not mean it will outperform the Series 11 in every type of workout.
The result also adds an independent reference point to Apple’s own study. Apple reported that the Series 12 was statistically more accurate than competing wearables in 139 of 159 comparisons. Because that study was conducted and funded by Apple, Ter Horst’s separate testing offers another way to assess how the sensor performs outside Apple’s own testing environment.
The Step Counter Also Holds Up
Heart rate was not the only sensor Ter Horst put through its paces. He also manually counted roughly 5,000 steps during a walk and compared the total with the Series 12.
The watch came reasonably close to the manual count, although it showed a slight tendency to overcount steps.
The New Sensor Looks Strong, With One Important Caveat
The Series 12’s first independent test gives its redesigned heart rate sensor a strong showing. Its readings came remarkably close to the Polar H10 during indoor cycling and remained highly correlated during running and weightlifting.
The Series 11’s better running result is the important caveat. The test does not show that the Series 12 is universally more accurate than its predecessor, but it does show that Apple’s new sensor can deliver readings that closely track a dedicated chest strap across several demanding workouts.
