For great abs, you need two things: A little knowledge and a little action.

Start with the knowledge. The first thing you should know is that crunches are a lot of pain for little gain. True, they will shape and tone the outer layer of abdominal muscles but shaping jelly still only gets you well-shaped jelly.

There are three layers of abdominal muscles, and the only way to get killer abs is to work the deepest layers: the transverse abdominus and the lateral obliques.

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The transverse abdominus is the muscle you feel when you sit still and tense, as if someone is going to punch you in the gut.

The lateral obliques are the ones you feel when you tense and twist slowly to one side.

That's the knowledge. The action is even easier.

There are a number of exercises you can do to work the deepest layers of your abs. But they're boring, and doing them for 5 minutes feels like an hour. They're also not as effective as the three following activities: