Such a deal... And also a great core workout for those really wanting to get into it. (kaanapaliresort.com)
A lot of core workouts also involve being in the plank position, and this is great for your shoulders and upper body too! (rachaelattard.com)
You can get a great core workout from more traditional bodyweight movements, however, adding an implement to your core training will up the ante on your next ab workout. (onnit.com)