Crunch sideways off the ball to torch your obliques.
Bend straight to the side, do not twist, and keep the ball from rolling.
Lying sideways over the ball drapes your obliques over its curve, so each rep starts from a genuine side stretch that lying on the floor can never provide, then contracts the ribs toward the hip through a full arc. Working one side at a time means the top-side obliques do all the lifting while the bottom side controls the ball. It is the go-to for direct oblique work that trains lateral flexion through its complete range.
The floor stops your torso at flat, the ball lets you bend sideways over its curve first. That starting stretch is the whole advantage, your obliques work through range a floor side crunch physically cannot reach.
Stagger your feet wide and brace the lower one against a wall if you have one nearby. A stable base lets you crunch hard instead of spending the whole set fighting to not fall off.
No, this is pure side bending, ribs straight toward hip. Adding a twist changes the exercise and usually means momentum has crept in, keep the movement in one clean sideways plane.
