Use the BOSU ball to elevate your upper body as you do an oblique side crunch. Balancing on the ball will require using the stabilizer muscles in your abs and back, working the entire complex supporting your obliques.
Lie on your side on a BOSU ball with the ball under your rib cage to just above your hip. Your shoulders will extend beyond the ball. Bend your elbows and put your hands lightly behind your head, so that your bottom elbow gently rests on the floor and your top elbow extends toward the ceiling. Put your legs in a scissor position for balance, with your bottom leg slightly forward and your top leg back. Turn the toe of your top leg upward slightly, so that you have a stable balance through the back leg (see Photo 1).
- From the starting position, perform an oblique crunch. Take your top elbow toward your top hip by contracting the muscles just above your top hip. Keep facing sideways through this movement—try not to rotate your shoulders toward the ceiling, as this will redirect the effort away from your obliques. Try not to use your legs for leverage, only for balance (see Photos 2 and 3).
- Lower yourself back to the starting position, being sure to let your top side stretch at the bottom of your motion before repeating the crunch (see Photo 4).
For a more difficult variation on this exercise, take a dumbbell in both hands, held by the ends, and extend both arms directly overhead. Lower your arms until they are parallel to the floor, and, from this starting position, perform the oblique crunch, bringing both arms toward the ceiling as you contract your obliques.
About Mike Clausen: Clausen is the founder and co-owner of DIAKADI Body training gym, voted best personal training gym in San Francisco by CitySearch in 2006. He has been actively involved in sports and weightlifting since high school, and continues to use that knowledge when training his clients. Clausen is both A.C.E. and N.A.S.M. certified and has been training clients professionally for six years. He enjoys making his clients stronger, both physically and mentally, giving them the tools to create an efficient body and to do things they thought were not possible.