Position thighs prone on padding. Hook heels on platform lip or under padded brace. Place barbell on back of shoulders and grasp bar to sides.
Lower body by bending waist until fully flexed. Raise, or extend waist until torso is parallel to legs. Repeat.
Position pad high enough to evenly distribute body weight on thigh but not so high that range of motion is limited; abdomen should not press on top side of pad when upper body is lowered. Begin with body weight and add additional weight gradually to allow lower back adequate adaptation.
Maintain barbell's position on back of shoulders when upper body is lowered. Do not pause or bounce at bottom of lift. Do not lower weight beyond mild stretch throughout hamstrings and low back. Full range of motion will vary from person to person. Although articulation of waist is emphasized, some hip extension may accommodate movement. Also see Barbell Hyperextension and Barbell Back Raise.
Synergists (see comments)