If you've already mastered basic core-strengthening exercises like planks, I recommend mixing up your ab workouts by adding more advanced moves into your routine (but keep doing planks because they're great).
One move that I love, and slightly despise because of how much it challenges me, is ab circles. It works your six-pack muscles, transverse abdominis (the deep core muscles that act like a corset and stabilizes your spine and pelvis), and there's a little bit of oblique action involved, too.
You're 100 percent going to feel all of your ab muscles turn on after a few reps of ab circles. Along with eating quality foods and consistent exercise, this move will have you on your way to sculpted abs.
For this exercise you'll need a pair of core sliders or a medium-sized towel.