Re: Exercises....question regarding...
Thin--Mainly depends on what exercise you're doing. You may want to try getting a mat, but, for most such exercises, You want to have a relatively firm, flat surface (but doesn't need to be rock hard). Particularly for things like pelvic tilts, you want to know when you get to the floor and, for most people, don't want to overflex your back by pushing it into a too soft mattress. Again, though, it depends on your particular problem and what the exercise is. I know people who do a whole routine before they get out of bed (it's the only way they can!)