Roller Coaster Warning

A heavily bandaged man was sitting up in bed at the hospital when his friend came to visit.
“What happened to you the friend asked?”
“Well, we went to the amusement park and decided to ride the roller coaster. As we came to the top of the highest loop, I noticed a sign by the side of the track. I tried to read it, but it was very small and I couldn’t make it out. I was so curious that I went around again, but we went by so quickly that I still couldn’t see what the sign said. By now I was determined, so I went around a third time. As we reached the top I stood up in the car to get a better view.”
“And did you manage to see what the sign said this time?” asked his friend.
“Yes, remain seated at all times!”