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You long ago replaced crunches with planks, and smart move. But if you only alternate between full planks, forearm planks, and side planks, you're missing out on the true benefits of this core-strengthener.

This workout synergistically combines instability and dynamic plank exercises to trim and slim your middle while improving posture so you naturally look even thinner.

How it works: Complete all exercises back to back with little to no rest between. Do the workout on its own or at the end of another routine for a great abs-flab-busting finish to your workout.