What is curl-up (arms crossed)?

Curl-up (arms crossed)

1. Lie on your back on the floor, with your knees bent and your feet flat on the floor. (Or you can lie on any flat surface, such as a bed.)
2. Cross your arms over your chest. If this bothers your neck, try putting your hands behind your neck (not your head), with your elbows spread apart.
3. Slowly tighten your belly muscles and raise your head and shoulder blades off the floor. Keep breathing normally and don't hold your breath.
4. Keep your neck straight and do not press your chin to your chest.
5. Hold for 1 to 2 seconds. Then slowly lower yourself back to the floor.
6. Repeat 8 to 12 times.