To perform Medicine Ball Knee Ins, start by lying flat down on the floor with the feet flat and knees bent. Hold a medicine ball above the head at eye level with your your arms straight and over your head. With your feet 8-12 inches apart, pull in your knees until they are are directly over your hips. Your lower legs should be horizontal to the floor and your knees should bend at a 90-degree angle. Lower to starting position until your feet almost touch the floor and then repeat.