This movement was inspired by multi-tasker Christian Thibaudeau, who likes to save time by doing multiple things at once. One day, while simultaneously urinating and brushing his teeth, Christian had a eurekamoment:
Why can't I work my rectus abdominus, my obliques, and my serratus at the same time?
The Serratus Crunch was born the very next day.
Strengthening the serratus will help reduce the risk of shoulder injury and will actually increase your bench pressing strength by stabilizing the shoulder blades. Building your abs, of course, will keep women mesmerized as they trace their fingers along the deep nooks and crannies of your abdominal crevices, you big Wolverine, you.
The key point is to keep the arms perpendicular to the floor at all times. As you "crunch" your torso up, you should reach for the ceiling and try to bring the hands as high as possible. Hold that position for 2-3 seconds. If it's too easy, try it with your feet off the floor.
Now get to the gym and multi-task.