Sit on floor with knees bent and feet ... says Stewart. Lie face-up on floor, holding a medicine ball between your hands above chest. Bring knees into chest, shins parallel to floor.

Don't know what to do with that medicine ball? Here are 23 of the best medicine ball exercises from a trainer to strengthen ...

Once you feel comfortable that you’ve built enough foundational core strength, you can practice a more accessible variation ...

Half sit up Sit up straight with your knees bent and ... to your body to make the exercise easier or hold a dumbbell or medicine ball for extra intensity. 9. Beast with shoulder tap Get on all ...