Crunch on a tilt to torch your side abs.
Feel the squeeze in the obliques on the down side. Don't twist, just crunch up.
Dropping both knees to one side tilts your pelvis and puts the obliques on the down side in the perfect position to do the crunching, so a straight-up shoulder lift becomes side-ab work without any twisting. The range is short and the target is specific, which is exactly the point. It is the simplest floor drill going for isolating the muscles along your sides, one side per set until you switch.
The knee drop has already rotated your lower body, so a straight upward crunch loads the obliques by position, not by twisting. Adding a twist on top usually just drags the neck and shoulders around.
Along the side of your waist on the same side your knees are dropped toward. If you only feel your neck, stop pulling on your head and let the shoulders curl up on their own.
Yes, finish the full set on one side, switch, and match it. Uneven side work is how you build a trunk that rotates better one way than the other.
