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Stability Ball Increases Abdominal Activation
By Ryan Halvorson

The stability ball is the most offered piece of equipment in fitness facilities today, according to the 2007 IDEA Programs & Equipment Survey (IDEA Fitness Manager, (2007; 19 [4], 7-16). This comes as no surprise as you'd be hard-pressed to find a gym without one. But is all the buzz surrounding the stability ball unbalanced or does the hype hit the mark? According to researchers in the Department of Kinesiology at Occidental College in Los Angeles, there is a solid foundation for the popular piece of equipment. The study, which was published in the May issue of The Journal of Strength and Conditioning Research (2007; 21 [2], 506-09), set out to determine whether the stability ball offered greater abdominal activation than the traditional floor-based crunch, and whether changes in ball placement had any effect. Forty-one apparently healthy volunteers with an average age of 20 were fitted with electromyographic (EMG) equipment and then instructed to execute the exercise (lift head, shoulders, neck and shoulder blades from the ground) on the floor, and then to mimic the same movement as closely as possible while positioned atop the ball. According to EMG reports, crunches performed on the stability ball showed significantly greater abdominal activation than its more "traditional" counterpart. The results found heightened activity in the upper rectus abdominis, lower rectus abdominis and external oblique activity by 31%, 38% and 24%, respectively, when compared with the traditional crunch. When testing two different ball placements, researchers found a sharp decrease in abdominal activity when the ball was positioned below the scapulae as opposed to the lower lumbar region of the spine. According to study authors, these findings not only give credence to the stability ball as a viable piece of equipment, but will also provide trainers with an effective method for helping clients progressively improve abdominal strength. "For those with abdominal muscle weakness, a high ball placement will allow them to perform the crunch motion with less effort than when performed on a stable bench or floor," writes Sternlicht, et al. Once strength gains have been achieved, the trainer can then progress to floor crunches or change ball placement for a more challenging crunch.