@ColleenBerbeka Thanks for stopping by!
Your device detects activities based on the motion on your arm. The automatic detection is a feature called SmartTrack and it requires constant movement for usually at least 10 minutes to detect an activity(you can change this but 10 minutes is the minimum required). For example when using the elliptical machine make sure you have the moving bars so your device detects the motion and records the activity itself, once an Elliptical activity is saved on your account it should show on the Recent Exercise area. The same is when you are swimming so please keep the motion for at least 10 consecutive minutes. If your heart rate is high but there isn't much motion (yoga, weight lifting, etc.) then these activities will be difficult to be detected by your device. Still you can manually log your activity so you have a record on your account.
Hope this helps.
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