Turn off screen when exercising

Hello

Thank you for using Apple Support Communities.

We understand that you do not want to see the time on your Apple Watch when you are exercising. It sounds like you want to turn off the Always On feature of the Apple Watch. You can take a look at this support article on the Always On feature, which includes how to turn it off if you don't want to use it:

Use the Always On feature with your Apple Watch Series 5 - Apple Support

You can also use the Power Saving Mode on the Apple Watch to turn off the display:

"Save power while you work out

To preserve your battery life on long walks and runs, you can use Power Saving Mode to turn off the Always On display, the heart rate sensor, and cellular data. Your Apple Watch still calculates active calories, distance, pace, and elapsed time.

Here's how to turn Power Saving Mode on or off: 

1. On your iPhone, open the Apple Watch app. 
2. Tap the My Watch tab, then tap Workout.
3. Turn Power Saving Mode on or off."

From: Work out with your Apple Watch - Apple Support

Best regards.