In addition to increasing flexibility for crunches and additional abdominal exercises, the balance ball also improves balance and coordination. You can start with the basics such as regular crunches or oblique crunches. After mastering crunches you can proceed to something more challenging such as piques or roll-ins. In roll-ins and piques your feet are placed on your golf ball while your hands are on the floor. The stability ball ab exercises are a great addition to your ab workout. #2 The Medicine Ball The medicine ball is a weighted ball simply. Although some cultural people may believe medicine balls are just for boxers and sports athletes, medicine balls really can enhance your core workout.