Starting position: spine extended to hover above the ground with the butt planted, knuckles together, head rested upon fists.
Extending the elbows, maintaining spinal extension, knuckles still together.
Still extending the elbows while maintaining spinal extension, knuckles still together.
Full RoM of Rep: no need to lock out elbows by external rotation of the shoulders, knuckles still together, upper back making light contact with the deck, then from here relax back into starting position while maintaining spinal extension.
I call them #bridgeExtensions. It's basically a no-bull cousin of the back-bridge pushup in which you extend the spine with the butt planted and knuckles together behind the head and simply extend the elbows until the upper back touches the deck and then ease back into the starting position.