The on-screen metrics can be turned On or Off from the Display settings in the workout settings panel. Click or tap the gear icon in the top right corner to access this screen, and select the Display tab.
You can select which metrics you would like to see on the screen by toggling them on or off.
If the data from your sensor does not appear on the screen and the metric is turned on, check your sensor connections.
Turning them off will not prevent them from being saved to the workout file, provided that the sensor is connected on the Devices Tab.