It's time to tone your abs standing. Writing out the alphabet with a medicine ball will work your entire core from almost every conceivable angle. This standing exercise counts as functional fitness and burns considerably more calories than lying on the ground just crunching your upper abs. Grab a ball and get ready to be school your abs with the A, B, Cs.

There are two variations of this exercise, one for core stability and one for torso mobility. To start, grab a medicine ball between five and 15 pounds. Stand with your feet shoulder-width apart, making sure your knees are not locked.

• For stability: start with the ball at chest level, and slowly write the cursive alphabet in front of you. While your arms move around in all sorts of angles, you need to use your abs to keep your torso still. Think of keeping the area between your ribs and pelvis solid. For a more advanced version, try this move while standing on a BOSU.
• For mobility: start with the ball at chest level, but increase the range of motion of your arms making your alphabet larger and using your torso and rib cage to write the letters as well. Keep your abs engaged the entire time and start with a lighter medicine ball. For more of a challenge, try this version in a squat or a lunge.