Can anyone recommend some good ab and stomach exercises that are fairly low-impact on the back? I've got a horrible bad back, and can't do situps.

I cant do sit ups either, not cuz of my back tho, b/c Im not strong enough lol I can do crunches tho I dunno if those would be any easier on your back, maybe you could pilates?? It is good for your abs, and the rest of your body Im not sure what it would do to your back tho...it might help or make it worse...I dunno sorry

have you tried doing the "plank". I guess that's what it is called. My BF does this for his stomach & he has a 6 pack. He gets down on the floor like he's going to do a push-up but his forearms are on the floor & he holds this position for as long as he can. Make sure your behind is lower...I tried this & didn't feel anything because my behind was not low enough.

OHHHHH yes, ISOABS!! So called because they truly isolate your abdominals. However they also use your hams, glutes, and back to support you in that plank position, so I'm not sure if the OP would be okay with them--but you could certainly give them a shot!

I assume you meant you cannot do crunches, as situps are bad for you anyway. If not, have you tried crunches? What about ball crunches, where you lay on the exercise ball and crunch? What about this: you lay on your back, legs together and up, toes pointing towards the ceiling. Have a friend stand at your head and hold onto their ankles to keep yourself steady. Then your friend kinda pushes your legs down towards the floor, and you have to stop them from hitting the floor and bring them back up. Repeat. Could do this at an angle to work more obliques, otherwise this is good for lower abs.

Is your back problem an injury or a weakness? You may need to start with strengthening your back, then you can work on your core.

Not being sure of what back problems you exactly have, it may not be a good advice, but I'm still going to give it I have problems with my lower back, that made doing situps extremely painful (but it's alright, as they're not good anyway) so I tried another way of working my abs, that didn't involve such a strain on the back. I tried the first method described here, and it seems to work, because I can really feel my abds "working", as well as not hurting when it comes to the back.

If you want, you can also have a look at this page, it's a "Abds FAQ", perhaps you can find another exercise that suits you there.

my problem isn't so much that my back isn't strong, it's that from right below my breasts down to the hips it is basically fused, and therefore not flexable. It could probably use some strengthing too, but it's just soo inflexable!