Alright guys, I'm trying to get back into some kind of shape here, but I'm having a hard time figuring out what sorts of exercises I can do. Or rather, what's left that's allowed

I can do hip bridges with the pilates ball but they didn't give me much else that's still effective in PT. (I was doing "marching" while lying on my back but now that I'm strong enough to pick my feet up it's too easy!)

So, do any of you have core/ab exercises that don't involve flexing through the upper spine or doing anything that crunches those pesky screws in my upper back into the floor? Standard situps and crunches are forbidden.

Thanks!