One thing my trainer tried with me last week was hanging me upside down. He was getting tired of me lying on the floor and throwing my legs to the side to crack my back, so he thought hanging me upside down would get the pressure off my spine and help. And it just so happens he has the handy dandy leg cuffs with hooks on them. The first time I did it I was still a little ill and so couldn't remain in that position for long. But I did have enough time to do some upside down stomach crunches - basically lifting my torso up as high as possible.
Although I hate being upside down, I liked how I felt afterwards so I asked to do it again this week. I lasted longer and managed two sets. This time I did bicep and tricep curls upside down. Which is so weird. And, I also was supposed to do upside down squats. Think about it - something you take for granted is gravity, and when you are working against gravity, your whole world is turned upside down, literally. It is really really difficult to do. But, because it's so strange, I really like it, so hopefully I'll do it more.