Hey Pooka.

I assume you are anchoring your feet and elevating your torso by flexing it towards your knees.

Two things:

1) It will not build muscles in the wrong places - and no, it won't make your abs protrude like a pro-bodybuilder on a lot of steroids.

2) I would not do recommend this move. I know it hits the abs hard, but it also tends to work the hip flexors a lot and the iliopsoas muscles. Most people have tight hip flexors. Doing this exercise without stretching the hip flexor or exercising the hip extensor might cause trouble by pulling in your back muscles. This might be a contributing cause to lordosis and back pain.

There are plenty of alternatives for that. Have you checked TrainerDan's site?

Oh, and do hyperextensions for your lower back.

Good luck,

Loony