1.3K views · 22 reactions | How To Do The BOSU Crunch! If you want 6 pack abs you must add resistance training to your ab workout! You must train abs just like biceps. Using the BOSU Ball, you can sit about a 1/4 way on the ball with a weight in your hands. Lean back hyperextending the back, then slowly flex the abdominals coming up into a crunch. This is how you develop visible ab muscles. Of course, you gotta cut that body fat as well!!! | Expect Results Fitness | Facebook