Here is an actual exercise I used to follow up my on table manual muscle energy technique for an injured athlete. The athlete had hurt his back doing a maximal deadlift while I was down in Florida with GAIN this past June. By the time I got to him a few weeks later he had no lordosis in his spine and a left lateral shift. My evaluation revealed a type 2 dysfunction of his lumbar spine. Nomenclature it L3 ESRL. That is, lumbar vertebrae 3 was stuck extended, sidebent, and rotated left.
The exercise is a right side lying modified (bottom knee bent to shorten the lever arm) rotational plank. We're using gravity to gently mobilize the spine through muscle contraction, yet prevent the trunk from going through the interbarrier zone of the injured joints; in all three planes. In other words, the body position, ground, and gravity are blocking the body from where it can't go yet. The starting position takes us deeper into the dysfunction so we can use the explode out of it to assist the correcton.