Backwards sit-ups?

[Paroxysm1]

Backwards sit-ups, seated exercise, and yoga?

I'm obese-- 240 lbs with a BMI of about 42.

I started out doing sit-ups... but then I noticed that my back was popping.
So I switched to crunches.
My back stopped popping, but now my tailbone is sore and my neck starts to hurt as well.

So I looked up backwards sit-ups.

"Not everyone is capable of doing sit-ups, and those who are capable of doing sit-ups are at risk for neck and back injuries. Backwards sit-ups are a safe alternative to standard sit-ups, and they can be every bit as effective. Backwards sit-ups tighten the lower abdominal muscles and burn calories the safe and easy way.

Lie on the floor with your knees bent and your palms facing downward beneath your buttocks. With your legs together, draw your bent knees toward your upper body. While your knees are perpendicular to your body, straighten your legs. When correctly doing this easy exercise you'll feel your lower abdominal muscles tightening. After a second or two, bend your knees, and slowly bring your feet back down to the floor.

Do at least 10 backwards sit-ups, and complete another set of 10 if possible. Each week, increase the number of backwards sit-ups you do. Your abdominal muscles will become increasingly tighter as a result, and you'll burn numerous calories in the process."

Does anyone do these?
Do they really have the same effect?
I have tried a few, and maybe I'm doing it wrong, but it doesn't seem quite the same.

I found this site with seated exercises, and it seems good. I have 5 lb weights that I use for the last ones:


I'm also thinking of using yoga. Would I be able to do this even with my weight?
I found this site with postures:

 

[Michelle01]

the exercise you describe, I do something pretty much the same in my pilates video. though, for abs, another I like that might work for you is sitting on a chair, bringing legs straight out, then bringing them in to the chair, leaving the feet at the same height as the seat of the chair.

I think, if you want to try yoga, you should. If it doesn't help, then replace it, but you'll never know if you dont give it a try.