While recording an exercise you can lock the buttons by keeping the lower button pressed and then select Lock. Once locked, you cannot perform any action that requires button interaction (create laps, pause/end exercise etc.), but it is possible to scroll the display views and you can turn on the backlight with any button press if the backlight is in automatic mode.
To unlock everything, keep the lower button pressed again.
When you are not recording an exercise, the screen locks and dims after one minute of inactivity. To activate the screen, press any button.
The screen also goes to sleep (blank) after a period of inactivity. Any movement turns the screen on again.