Seated Russian twist
This exercise works on your abdominal muscles. keep your heels touching the ground if you are a beginner. Keeping the back straight, lean back to a 45degree angle and extend the medicine ball in front of your chest. Rotate slowly from side to side, keeping the arms long and the back straight. As you progress, you can lift your legs in the air for a harder wokout if you feel challenged. Try 10 repititions each side.