Lie supine (on your back) on an ab bench. Your hips and knees should be at 90-degree angles.
Position your hands behind your head and hook your feet under the rolls to lock in your position.
Press your lower back against the bench.
Execution
Keeping your neck neutral and lower back pressed against the bench, exhale as you lift your head and shoulders off the bench.
Hold for a count of two.
Inhale as you reverse the motion and return to the starting position.
Repeat for the desired number of repetitions.
Comments and tips
The 90-degree crunch is safer on the lower back compared to the standard crunch. This is because the 90-degree angle of the hips helps prevent the lower back from arching.
Keep your elbows out to the sides throughout the whole exercise. If you are bringing your elbows in, you may be using momentum or using your neck flexors to crunch instead of engaging your abdominals.
Do not tuck in your chin. This will recruit your neck flexor muscles instead of your abdominals.
To make this exercise more challenging, extend your arms over your head or hold a medicine ball with both hands.
To make this exercise easier, cross your arms over your chest or keep them by your sides.
If you do not have an ab bench, you can use a flat bench instead. Lie supine on the floor, then bend your knees and place your lower legs on the flat bench.
