If happens because of our imbalance. Balance begins in our ears, which is a balance centre that sends messages to our brain. The messages tell us in which direction we are moving and how fast. That is how we are able to maintain our balance. While swinging, however, our body moves in different directions and the message does not stay. It puts strain on the brain and it gets confused. That is, when we feel nasty in the stomach. The same feeling can also come on a roller coaster or even in an elevator.