This is the most popular, yet one of the most dangerous abs exercises.
Lie down. Bend your knees and put your feet on the floor firmly.
Place your arms behind your head or cross them on the top of your chest.
As you inhale, arch your back a little stretching your abs muscles.
Keep your neck stationary.
As you reach maximum contraction, exhale and lift up the upper body while crunching your back and bringing your shoulders closer to your waist.
Don't move your shoulders.
Reach the maximum contraction of the abs, hold this position for 2-5 seconds and return slowly to the starting position.
Don't bring your elbows forward and don't hold your arms behind the head. Thus, it will be easier to perform exercise.
To keep your neck stationary, imagine that you are holding a small ball with your chin.
If the exercise is too easy for you, you can hold a barbell plate or a dumbbell over your head.
You can get a better foothold by placing them against the wall.
This exercise works the iliopsoas muscle mainly.
You can make this exercise more difficult by twisting to the sides (to the right and to the left for the obliques) after reaching the top, if you don't have back pain.