Sharpen Your Six-Pack

With Stability Ball Crunches

By Stephen E. Alway, Ph.D.

By now, everyone knows in order to get sharp abdominals, it’s important that to increase your metabolic rate through exercise, clean up your nutrition and be consistent with cardio. Training your abs efficiently is another part of the equation, of course.

The best abdominal exercises will shorten and tighten the fibers in the abdomen wall. Crunches on a stability ball are great because they optimize abdominal contractions while protecting the back. With the ball positioned correctly, you’ll feel a great burn and gut-ripping contractions.

Sharpen Your Six-Pack With Stability Ball Crunches


The muscle fibers of the rectus abdominis muscle are split into left and right halves by the linea alba, a thin, tendon-like vertical line. Usually there are three or four rows of horizontally-placed tendons running across the rectus abdominis. The short fibers of the rectus abdominis run from one horizontal tendinous insertion to the next. When the rectus abdominis is tightened and contracted, these short fibers bulge between the tendinous grooves, almost like small ropes or blocks— and this creates the six-pack look.

If both right and left halves of the rectus abdominis muscle contract, the trunk is flexed forward so that the head and chest move closer to the hips and legs (assuming a fixed pelvis). This is the general movement of the crunch. Although there is muscle activity in all of the blocks during most abdominal exercises, the upper two rows preferentially contract and shorten the most when doing crunches. However, in the crunch on the ball, the inferior fibers close to the pelvis can be activated effectively.

If you cannot see your external oblique muscles dance and tighten on the side of your waist, especially if you twist to either side, then ball crunches will move you a little closer to this goal. The muscle fibers in the external oblique run from the lower ribs, then unite with other slips of muscle fibers from the external oblique to form a flat fan-shaped muscle that attaches to the iliac bones of the pelvis and hip structure and also the linea alba. When both left and right sides of the external oblique muscles work together, they flex the trunk and move the head toward the feet. When one side contracts (unilateral contraction), the body twists to that side.

The internal oblique muscle sits just deep to the external oblique muscle. It attaches on a thick connective tissue sheath in the lower back called the thoracolumbar fascia and from the iliac bone of the hip. Its fibers run around the side of the trunk at right angles to the external oblique muscle, fanning out and running toward the head (superiorly). It attaches on the lowest three or four ribs. Similar to the external oblique muscle, if both left and right portions contract together, the internal oblique flexes the trunk at the waist and moves the head toward the feet. It assists in twisting the torso if it contracts unilaterally.


This exercise will most effectively contract the upper two rows of the rectus abdominis, but the internal and external oblique muscles will also assist in the flexion of the trunk.

1. Lie back on a stability ball, bending your knees and lowering yourself so that your shoulders and back are lying along the center of the ball.

2. Extend your knees and let the ball roll a bit toward your feet, until your knees are about 900 and the ball is lying in the small of your back (lumbar region). Your shoulders will not touch the ball, but your shoulder blades will contact the ball in the starting position. Make very sure that your shoes have a good gripping surface; otherwise, you may risk sliding off the ball during the exercise.

3. Place your fingertips over your temples on either side of your head. It is not a good idea to place your hands behind your head and interlace the fingers, because as you fatigue you could pull up on the head with your hands and forcefully bend your neck forward.If your fingers are placed on the side of your head (the temple area), you cannot use your head as a lever to help you lift your head and torso from off of the ball.

4. Point your elbows to the side and away from your body (not pointing forward). Take a breath, and then exhale as you bring your head and chest upward toward the ceiling. Your shoulders should raise an inch or two during this first phase and you will feel your lower back press deeper into the ball and the upper row of rectus abdominis will contract strongly as you come up. Do not let the ball roll forward as you come upward. Also, make sure that you do not allow your hips to drop down as your chest comes upward.

5. During the second phase of the crunch, try to come up even farther so your shoulder blades (scapula) lift off of the ball. However, as you raise your torso, you should think about curling your shoulders and upper back so that your chin moves toward your chest as your upper body is curling (or crunching) toward your thighs. Hold the crunched position for a count of two and tense your abdominal muscles in this position.

6. During the third part of the exercise, tilt your pelvis forward and upward toward your head as your shoulders move upward. The ball position and pelvis tilt are critical for strongly activating the lower row of your six-pack. Squeeze your abdominals for another 3 seconds while tilting the pelvis. These isometric contractions will place the finishing intensity factor into activating the fibers of your abdominal wall.

7. Inhale as you slowly control your upper body during its return toward the starting position. The ball prevents your shoulders and head from resting between reps so that you will maintain tension throughout the entire exercise and between reps. This greatly increases the effectiveness and intensity of the exercise.


Studies have shown that, on average, abdominal muscle activity doubles when the ball is moved from the upper to the lower back position. This suggests that a stability ball is not only effective for training the abdominal musculature, but when it is correctly positioned in your lumbar region, the abdominal muscle activity is much greater when compared with a traditional crunch.

Bird M, Fletcher KM and Koch AJ. Electromyographic comparison of the ab-slide and crunch exercises. J Strength Cond Res, 20: 436-440, 2006.

Escamilla RF, Babb E, DeWitt R, Jew P, Kelleher P, Burnham T, Busch J, D’Anna K, Mowbray R and Imamura RT. Electromyographic analysis of traditional and nontraditional abdominal exercises: implications for rehabilitation and training. Phys Ther, 86: 656-671, 2006.

Moore KL and Daley AF. Clinically Oriented Anatomy, Lippincott Williams & Williams, Baltimore, 4th Edition pp. 1999. 178-187.

Sternlicht E and Rugg S. Electromyographic analysis of abdominal muscle activity using portable abdominal exercise devices and a traditional crunch. J Strength Cond Res, 17: 463-468, 2003.

Sternlicht E, Rugg S, Fujii LL, Tomomitsu KF and Seki MM. Electromyographic comparison of a stability ball crunch with a traditional crunch. J Strength Cond Res, 21: 506-509, 2007.

Sternlicht E, Rugg SG, Bernstein MD and Armstrong SD. Electromyographical analysis and comparison of selected abdominal training devices with a traditional crunch. J Strength Cond Res, 19: 157-162, 2005.