My Friend Has A Machine That Uses For Her Back.

My friend has a machine that uses for her back. She turns upside down on it. I tried to use it, but when I was upside down, I felt horribly sick to my stomach and became extremely dizzy. Became better once I was rightside up. Then the other day, I was bent over and had to look up from a bent position and had the same sensation. I have occasional dizziness but have had only one episode of true vertigo many years ago. Thanks for your help.