Just got an interesting study in this month's Journal of Strength and Conditioning Research. Here's the abstract: J.L. Nuzzo, G.O. McCaulley, P. Cormie, N.T. Triplett, J.M. McBride, Appalachian State University, Boone, NC. PURPOSE: To investigate the amount of trunk muscle activity during three stability ball exercises in comparison to the squat (SQ) and deadlift (DL). METHODS: Nine resistance-trained males participated in one testing session. Isometric contractions of three seconds were performed during the stability ball exercises (quadruped (QP), pelvic thrust (PT), back extension (BE)). In addition, SQs and DLs with loads of approximately 50, 70, 90 and 100% of one-repetition maximum (1RM) were completed. During all exercises, average integrated electromyography (IEMG) from the rectus abdominis (RA), external obliques (EO), longissimus (L1) and multifidus (L5) muscles was collected and analyzed. RESULTS: When expressed relative to DL 1RM, muscle activity was 19.5 Â± 14.8% for L1 and 30.2 Â± 19.3% for L5 during QP, 31.4 Â± 13.4% for L1 and 37.6 Â± 12.4% for L5 during PT, and 44.2 Â± 22.8% for L1 and 45.5 Â± 21.6% for L5 during BE. IEMG of L1 during the concentric phase of SQ and DL at 90 and 100% of 1RM was significantly greater (p < 0.05) when compared to all three stability ball exercises. Muscle activity of L5 during the SQ and DL at 100% of 1RM was significantly greater in comparison to all three stability ball exercises. Furthermore, muscle activity of L1 during the DL at 50 and 70% of 1RM was significantly greater than QP and PT. No significant differences were observed in RA and EO muscle activity during the SQ and DL at any load when compared to all three stability ball exercises. CONCLUSION: Activity of the trunk muscles during submaximal and maximal SQs and DLs is significantly greater or equal to that which is produced during stability ball exercises. The low level of back extensor muscle activity (L1 and L5) during the stability ball exercises indicates an insufficient stimulus to elicit gains in muscular strength and hypertrophy. As a result, the efficacy of stability ball exercises for improving athletic performance is questioned. PRACTICAL APPLICATION: The SQ and DL provide a significantly greater stimulus to the trunk muscles in comparison to stability ball exercises; thus, the use of SQs and DLs for improving trunk muscle strength is recommended. Interesting, I heard speculation on this but this is the first study I've seen showing it.