one of my fave exercises to do on an exercise ball is u lie on the ball with your shoulders & neck touching the ball and your body at a horizontal angle with your knees bent at a 90 degree angle, have a pelvic tilt as well. you then use free weights, one in each hand starting with your hands at level just above your chest and raising your arms at the same time to touch the weights together above your chest. Keep your elbows bent, dont lock out at the top. Its a great leg, arm & core workout. I do 3 sets of 15, and adjust the free weights as I get stronger.