I'm new to Garmin after years on Fitbit... I'm having some problems with heartrate tracking.
It seems to work fine when I manually start an activity (constant HR around 140), but doing exactly the same exercise when I forget to start the activity it does not do a good job (HR hardly gets above 90 for most of the session).
The following two graphs are doing exactly the same Eliptical workout yesterday and today.
Fitbit would not spot it as an elliptical session but would at least get the heart rate correct.
Any ideas why this may be happening on the Garmin?