Usually this sport is mostly done by men to get a six pack stomach. This movement is also very good for the spine, abdomen, arms and thighs.
This movement is almost similar to sit-up exercise, it's just that the ab crunches movement is more focused on the state of the back that must remain attached to the floor so that it will produce more focused pressure around the abdominal area. As for the condition of the hands can be placed behind the head or can also be placed in front of the chest in a crossed position.