The most misunderstood and underused piece of equipment in any gym.
The back extension machine (should be called the hip extension machine). Most people will use this as a lower back exercise. Why wouldn’t they. It’s all they feel because they’re doing it wrong (unless, lower back is their focus). To hit the hamstrings the pad sits a little lower like in the 3rd video. This way I can fully flex at my hips and push my knees backwards at in the position where my hamstrings are longest, focusing on the stretch portion of the movement.
See in the first two videos the pad is set higher. It’s not so high that my lumbar spine has to flex when I fold over but it’s high enough so that my hamstrings aren’t having to hold my while weight, this lets me focus on my glutes at the top of the movement. Also notice that my knees are flexed almost like a Nordic hamstring curl (body weight hamstring curl). Notice my upper back is in flexion to reduce the chance of my lower back being the main muscle used to extend the hips.
Bare in mind the lower back has to work isometrically so it will be felt to some degree but should NOT be the over ridding feeling.