That looks like a prime candidate for what hurt your back. I could almost feel twinges in my back just looking at the photos. Hope whatever it is heals up quickly.
Don't you just love it when do something to get fitter and get injured during it? I hurt my foot once in yoga class, and after that I made sure I didn't go to class right before a race!
I have found all those belly exercises to be painful on my back. It just does not bend that way and can barely get my arms up doing them. I roll over and do crunches instead.
I can see value in doing *some* back exercises (to balance out the abs), but these were too much.
There is a lot of value. They are just really hard to do, and this one in particular does look a bit dangerous.
Hadn't looked at the pictures, only the first. That is about as high as I can get. The arms up position is one that truly amazes me. There is no way I could get that high. I will get my back exercise shoveling snow or turning over the garden and compost pile.