This is considered an advanced exercise ball exercise. One requires significant balance, control, scapular stability and abdominal strength.
A study published in the Journal of Orthopaedic and Sports Physical Therapy in January 2010 found that this exercise when compared to 7 other exercise ball exercises (roll out, decline pushup, knee ups, skier, hip extension right and left, and sitting march) and 2 traditional abdominal exercises (crunch and situps) was one of the best exercises for recruiting abdominal musculature and the core (lumbopelvic hip complex).
Repeat this ball exercise 5 times.
Repeat this ball exercise 10 times.
Repeat this ball exercise 15 times.