Place sandbag or medicine ball between ankles. Lay torso and waist on bench and grasp handles. Feet should be above floor with legs straight.
Raise weight by extending hips as high as possible until legs are nearly straight. Lower legs to original position. Repeat.
Exercise can be performed without added weight. Some individuals may be able to articulate both through the hips and through the lower back (i.e. lumbar spine), in which case, Erector Spinae also becomes synergist.