Settings of Apple Watch App

When you scroll down the top screen, there is a "Settings" button.

Zone Notifications

When the heart rate zone changes, it will inform you with notification sound and Haptic feedback.
If you do not want to be notified, turn off the switch.

Auto Pause

It stops and resumes automatically.
Turning off the switch turns it invalid.
When auto pause is ON, the pause button is not displayed on measurement.

This function is effective only when you select the following activities.

*1: watchOS4.2, Zones ver2.0, Apple Watch Serires3 or over

Other Settings

Heart rate zones, units, and custom workouts are set in the iPhone app.
iPhone app settings are automatically reflected in Apple Watch.
If the latest settings are not reflected, put iPhone and Apple Watch in a state that they can communicate and tap "Sync Now".

If the iPhone app is not installed, the "Sync Now" button is not displayed.