Want to Know What a Core-quake Feels Like? Try Jordan Chiles's and Simone Biles's Ab Workout

• In a seated position with your legs out long, lean forward and place your hands slightly past your knees. (The farther you place your hands, the harder it is.)
• Trying not to lean too far back, engage your core as you lift your legs a few inches up toward your chest.
• Lower back down to complete one rep, and do 10 reps total before holding this same position for five seconds.

Repeat this two more times.