Do this advanced take on a stability ball crunch and you'll have a tighter core in less than a month!
There are two elements that you need to incorporate into your abs routine if you want a tight midsection in little time: instability and weight. We’ve paired an unstable surface with a medicine ball to create an amazing exercise that will carve your entire core.
If you’re a beginner, master the move on the floor first before moving on the ball.