Adjustable Hyper Extension
A hyperextension or back extension is an exercise that works the lower back as well as the mid and upper back, specifically the erector spinae.
It may be performed using a Roman chair to hold the feet down and hips up or, without equipment, by lying face-down on the floor, and lifting the torso and arms together up off the floor. It can also be performed, in the bird dog exercise, in a prone position with arms forward. This version involves lifting one arm and the opposing leg at the same time, then releasing.
These strengthen the lower back and are ideal to be used after deadlifts for complete exhaustion of the lower back muscles.