Position
Lie face down on an inclined, flat, or declined bench or platform with your legs slightly rotated out and your knees slightly flexed. Place your arms next to the body, off to the side, or overhead, depending on the desired resistance. Begin with your head and chest raised slightly off of the bench to provide tension on your lower back muscles.

Technique
Contract your erector spinae. Slowly raise your trunk. Pull your shoulder blades together and down toward the gluteus. Continue to extend your back slowly, one vertebra at a time, to the point where your erector spinae is fully contracted without any spinal discomfort. Hold, continue to contract your erector spinae, and then slowly lower your trunk back to its original start position. Repeat.