What does "high energy ahead" mean?

High energy in the front means that during the playback of some videos, stimulating scenes will appear. For example, some animations have scary scenes at the end, and in some programs, when the climax is approaching, the barrage will appear before it. Someone will send "high energy forward, non-combatants evacuate quickly", and if there is a more severe situation, "nuclear energy forward" will be sent to remind them to be prepared.