Have you ever been caught up in a sudden surge within a crowd, when it all suddenly moves, temporarily sweeping you off your feet, making the pulse race a little more until you actually begin to enjoy the sensation?
It brings out a sudden rush of emotions. It can be intense, it moves you in a particular direction, often you are struggling to regain control, and everything around you heightens in your awareness. You love it or you hate it.
Either way it gives a real rush.