Heart rate doesn't record accurately on some activities - fēnix 5 series - Wearables - Garmin Forums
Garmin Fenix 5/5S/5X In-Depth Review | DC Rainmaker
Garmin Fenix 5/5S/5X In-Depth Review | DC Rainmaker
Garmin Fenix Optical Heart Rate Test | muppix.net
PSA: Look at the heart rate sensor of your fenix 5. Has it cracks like mine? If yes, it's a common problem. Send it to Garmin and get a free replacement. Do