Is there an alternative exercise for reverse curl crunch?

I'm following a set workout regimen and it calls for 40 reverse curls "To do: Lie on your back with your arms by your sides. Raise your legs toward the ceiling until they are perpendicular to it. Raise and then lower your two to four inches off the floor." I was wondering if there was some other exercise I could replace this one with and still work out the same muscles.