Since this is obviously a GIF, the speed of which is quite high but I could not slow it down but YOU MUST go slower.
Brief exercise description
Lay flat on the GluteHam developer as shown, on a flat bench, or the 45 degree incline bench, in a stretched out position, place your hands on your chest, from this position lower down and then use your lower back muscles to lift your upper torso up parallel, no further than parallel to the floor. Do not hyper-extend your lower back. Pause at the top for a moment then lower back down for another repetition.
Keep your head in line with your upper back and don’t extend it backwards.
If you have lower back issues speak to your health care professional before doing these.