When will Apple Watch use external device data?
When will Apple Watch use heart rate data from an external heart rate monitor (i.e. Polar chest strap via Bluetooth)? Is there a way to distinguish data from the watch versus from the chest strap?
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If you open Health, then select your Heart rate data, then scroll all the way down to the bottom and you will see under Options a link to Data Sources & Access. Tap on that, then you will see a list of data sources. You can tap on the source and it will indicate when it was taken and what the data is. The sources may be listed multiple times based on however long you have been using Health, but the sources will go back as long as you have been measuring your heart rate.