Nothing earth shattering here, but this is a superset-no-rest-between crunch to reverse crunch combo I really like and sharing just because.
The peak band tension in the crunch followed by the rather extreme loaded arch of the reverse crunch creates all kinds of fatigue burnout sensation that I just love / some clients love.
Just back and forth with minimal rest and go until can't go anymore.
(My back has no issues with any of the spine range).
I do this after the Freemotion Ab standing crunch + a seated row back extension superset "for dessert" before moving onto side bends & twists.