When people think “abs” they usually think of endless crunches or sit-ups, but it’s really way more complicated than that.What they really should be thinking about are moves that work the core — as in the entire core. These muscles are so much more than your six-pack (yes, everyone has a “washboard” they can be proud of, whether there’s some harmless padding on top or not), both in form and in function. Your core includes everything from the tops of your shoulders to the creases below your butt, from the outermost rectus abdominis (this is the muscle that looks like a six-pack) and side obliques to the deep stabilizers that support your spine. They’re also responsible for pretty much all coordinated movement — and non-movement — you do all day, from putting away groceries to sitting up at a desk.Therefore, the very best “abs” exercises work all those core muscles in one of two ways (or both): by facilitating movement or by stabilizing against movement.Ahead, we'll show you 16 moves that fit the bill. My advice (oh yeah, did I mention I'm a personal trainer?) is to choose three to five of these (ideally, one or two that target the front, sides, and back of your body, respectively) as a great core finisher to your regular workout.To make it a core workout all on its own, do that same number of moves as a circuit, one after the other, and repeat it up to four times through.