12/13/13 NOTE: I am republishing this as I found out that I accidentally published this as ‘private’ back in September. My apologies.
This CrossFit exercise was recommended by a friend. It really is harder than it looks. Try to do this for 30 seconds to a minute twice a day for days 10 – 14.
“You can thank the Crossfit crew for popularizing the “hollow rock,” a gymnastic staple, that’s a lot harder than it looks. When done properly, the hollow rock will strengthen your core better than just about any other exercise. Lie down face up with your arms and legs both extended and about one foot off the floor. The goal is to be the shape of a rocking chair. Then, much like a rocking chair, start moving back and forth while keeping your body stiff and without raising your arms and legs.” (Running Competitor)