Advanced Abdominals
Before commencing any of these exercises, you should warm-up your abdominal muscles with a combination of easier oblique - upper and lower abdominal exercises, followed by sufficient stretches of your abdominal muscles.
If your new to exercise, and are here to quickly develop a 6-pack, then you will cause yourself any injury. These exercises are only suitable for persons with strong developed core stability muscles, requiring further exercises to improve or gain muscular development.
Look at using the beginner's exercises, followed by the intermediate and oblique exercises prior to trying any of the following.