What Makes Apple Watches More Accurate Than a Polar OH1 Sensor?

Last Updated on September 20, 2022 by pg@petergamma.org

• Before Rob ter Horst started to test heart rate monitors, the Polar OH1 was known as very accurate if not the most accurate optical heart rate sensor on the market.

• Then Rob published plots of HRMs he tested, and found out, the most accurate devices are Apple watches and Huawei watches.
• An explanation that the Polar OH1 was more accurate than wrist based devices was it s architecture. It was a non-wrist based sensor and had more optical sensors. Wrist based watches are sometimes not fitted very tight to the wrist, which makes them inaccurate by causing movement artifacts.

• But then suddenly, Rob found out that for instance the wrist based Apple watches are more accurate than the non-wrist based Polar OH1 sensor.

• A hypothesis for this could be that Apple uses novel motion-artifact removal algorithms:

https://scholar.google.com/citations?user=OOhuA6gAAAAJ&hl=de&oi=sra

• In a picture from Rob ter Horsts Youtube video about the Apple watch 8, whe can see, that the watch has 8 holes at the backsite:

• In contrast, the Polar OH1 sensors, which already has been validated in a PLOS One paper with a gNautilus ECG reference device, has 6 green lights. In the paper, it s accuracy was roughly 95% compared to the ECG reference device:

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0217288

• the Polar OH1 is comfortable to wear, highly accurate, has excellent software support with MQTT app and Polar SDK. But still, it is not the latest device from Polar anymore. It has already a successor, the Verity Sense, which has not yet been validated by so many papers than the Polar OH1.

• For clinical an research applications, the accuracy of the Polar OH1 is in an accuracy range, which makes the device interesting for these applications. But this would require further testing. But who wants to further validate a device, which allready has a successor and competitors, which seem to be more accurate?

• Is it not possible to build a HRM sensor by ourself, which is highly accurate, and is not soon replaced by a successor which is more accurate?

• We are convinced that this is worth testing. How accurate is a recent open source heart rate monitor, for instance from DF Robot?

• How accurate is a device, when we combine 6-8 DF Robot sensors, and compare the accuracy to a Polar OH1, Apple Watch 8, Polar H10 chest strap or Equivital with LabChart Pro software?

• And what happens, when we additionaly use HeartPy software?

• Is this approach not more promising for physiolgists and eventually other persons, which are interested in highly accurate HRM sensors, than reviewing and testing which is currently the most accurate optical heart rate sensor on the market, and waiting for a successor which is again more accurate?