Fix the ankles in a glute-ham bench or similar adjusted to place the pad on the upper thighs. Bend at the hip and back to hang straight down from the hip—back relaxed and trunk hanging vertically.
 
Extend the hip and back together to bring yourself up to an extended position above horizontal in which the entire back, including the upper back, is extended completely and the glutes are forcefully contracted. Lift your head up at the top to reinforce upper back extension.
 
For unweighted back extensions, placing the hands behind the head is recommended to help encourage better extension of the upper back. For weighted back extensions, hold the weight in the form of a barbell or dumbbell behind the neck to ensure better resistance and better reinforce that upper back extension.
 
Notes
Technically, this execution is combined back and hip extension. Back extension can be isolated by fixing the hips in place with the glutes and flexing and extending only along the spine. This can be assisted by relocating the fulcrum or pad of the bench closer to the hips.
 
Purpose
The back extension both trains the activation of the spinal extensors and strengthens their ability to extend the back.
 
Programming
Unweighted back extensions can be performed every training day with about 3-4 sets of 10-15 reps. Weighted back extensions can be done 2-4 days weekly. Unweighted extensions and holds in the extended position can also be performed during the warm-up to encourage activation for the training session to follow.
 
Variations
The tempo of the movement can be changed, a pause in the extended position can be added, and rotation can be added during the extension or while paused at the top.