Lie supine (on your back) on an ab bench. If you don’t have an ab bench, lie supine on the floor, bend your knees and place your lower legs on a flat bench.
Position your hands either across your chest or behind your head or neck.
Press your lower back against the bench or floor.
Keeping your neck neutral, exhale as you slowly raise and twist your torso to one side by flexing your waist.
Hold for a count of two.
Inhale as you reverse the motion, return to the starting position, and fully relax your waist.
Repeat, but this time twist your torso to the opposite side.
Keep repeating and alternating the side to which you twist your torso.
Comments and tips
To protect your lower back, keep it pressed against the bench or floor. This is helped by having your lower legs elevated.
Keep your neck neutral. There should be lots of space between your chin and sternum.
Keep the movement slow and under control.
When performing the twisting crunch (or, for that matter, any kind of crunch), it’s important to fully relax your waist before each contraction. This will ensure that your muscles fully and dynamically contract during each repetition.
Make the twisting crunch more difficult by performing it on a declined bench or holding a plate either across your chest or behind your head.