The Crunch is an old school classic abdominal exercise. It works almost your entire abs region and is a good beginner movement. However, care must be taken to perform the Crunch correctly, as poor form can place undue stress on your head and neck. Since this is a floor-based movement, make sure to use a comfortable mat for your back.
Start by lying with your back and head on a mat or comfortable floor area.
Bend your knees so your feet are flat on the ground beneath you at about hip-width apart. Now place your two hands gently behind your head with your elbows flared out to the sides. Contract your abdominal region, exhale, and start to raise your upper body while keeping your feet and buttocks firmly on the ground.
Lift your torso up to about a 45-degree angle off the floor, then inhale and slowly lower yourself back down. This counts as one Crunch. Your back, neck, and head should lift up in unison and maintain a straight continuous line throughout the movement. Your neck and head should not be pushed or pulled up by your hands.
Your hands will be guiding your head and neck throughout the movement, but not using force to lift them. Do as many reps as you can until failure.