We were at lunch with friends yesterday and theri dd's gerbils spent an hour or more in those exercise ball things. It seemed really cruel to me - they kept bumping into chairs and things and they were going really fast and didn't seem to be able to stop. It must have been exhausting for them. And the bumping must have been really loud and jarring for a little animal like that. Am I being precious or have I got a point? I asked their owner how long it was OK to leave them in there and she said they needed the exercise!