This exercise provided courtesy of Billy Polson, founder and co-owner of DIAKADI Body training gym, voted best personal training gym in San Francisco by CitySearch in 2006.
Pikes and knees over a stability ball target the entire abdominal muscle, both low and high. Half the battle is controlling the return to the plank position, which is the start and finish of the exercise. You don't let go through your center at any point in this exercise—it's one long burn.
Take a push-up, or plank, position with your hands on the floor and a stability ball under your shoelaces (toes pointed), ankles, and lower shins. Use a stability ball of a size that allows you to be relatively parallel to the floor in this position, rather than feet high or shoulder high (see Photo 1).
- From the starting position, use your abs to fold your hips toward the ceiling in a pike, rolling the ball toward you with your feet as you rise. At the top of your motion, your hips will be raised high, with your shoulders and upper back pointing toward the floor, and only your toes touching the ball and holding it in place. You should be bent only at the hip, with knees straight and back flat (see Photos 2 and 3).
- From the pike position, slowly lower yourself back to the starting position, capturing the ball under the tops of your feet and your ankles as you descend. Be careful not to drop below parallel with the floor; use your abs to keep your hips and back flat (see Photos 4 and 5).
- Again from the starting position, contract through your abs and, keeping your chin down, bring your knees toward your chest in a tuck as you roll the ball toward you. The ball should stay under your shins and ankles, and your hips will rise as the ball comes under you. Using your abs to control your movement, roll the ball back out to the starting position, again being careful not to drop below parallel with the floor (see Photos 6 and 7).
- Continue to alternate pikes and tucks, returning to the plank position after each, for a full set of 20 of each, keeping your abdominals engaged throughout.