How To: Back Extension on a DEX or DEX II
Lower Back, Glutes & Hamstrings

From the inverted position, place your hands behind your head and contract your back and gluteal muscles and slowly lift your body from the bent position until nearly parallel to the floor. In the same slow and controlled motion, lower your torso until the top of your head is pointing to the floor. Then repeat.

Reps: 10 to 15
Sets: 3 to 5