Reverse the motion and isolate the lower abs.
Lift with your abs by curling the pelvis, not by swinging your legs for momentum.
Instead of curling your ribs toward your pelvis, you curl your pelvis toward your ribs, which shifts the emphasis onto the stubborn lower region of the abs. Lifting the hips by rolling the pelvis under, rather than swinging the legs, keeps the work in the core and takes the neck out of the movement entirely. It earns its place as the lower-ab move that needs zero equipment and zero momentum.
A regular crunch lifts your shoulders toward your hips, a reverse crunch lifts your hips toward your shoulders. Same muscle, opposite end doing the moving, and the reverse version biases the lower portion of the abs while sparing your neck.
You are swinging your legs up instead of curling your pelvis. Keep the knees parked over your hips and focus on peeling your hips off the floor with your abs. Smaller and stricter beats bigger and swingier.
They only need to lift a few inches, the magic is in the pelvis curling under, not in height. Then lower back down slowly, that controlled descent is half the exercise.
