Your core muscles engage with every push, pull, turn, and step you take. That’s why they respond so well to new challenges. It’s also why crunches are so boring—and ineffective.

“To work the abdominal muscles you have to do more than just flex and extend the trunk—you need to move through a variety of planes of motion and even incorporate resistance and force,” says Julia Ladewski, C.S.C.S., a strength coach and fitness expert based in Highland, IN. Using tools like kettlebells and medicine balls for resistance, and exercise balls and sliders to create instability opens you up to a whole new set of stimuli, she adds.

Try adding these moves to your regular routine—or put them all together for one rock-solid workout that’s sure to get results.

OUR MODEL: Alyssa Exposito
Profession: Personal trainer
Location: New York City
Instagram: @expossentials
Favorite Quote: “Where there’s a will, there’s a way.”