As the exercise ball increased in popularity, trainers and therapists began performing traditional resistance training exercises such as the bench press with dumbbells on an exercise ball. Theoretically, the unstable surface would increase activation of both trunk and shoulder muscles. In addition to the increased risk of injuries associated with traditional resistance training on an exercise ball, researchers began to show that using an exercise ball for extremity exercises was not as effective as once thought.

Canadian researchers (Andersen & Behm 2002) were among the first to show that performing a chest press on an exercise ball significantly decreased force output by 60%. Interestingly, the muscle activation levels remained the same between surface types despite a decrease in force output, suggesting resistance training on an unstable surface may produce less efficient muscle contractions. Subsequently, other researchers (Marshall & Murphy 2006) reported an increase in EMG levels of the deltoid and abdominals during a chest press on an exercise ball compared to a flat bench.  These conflicting results may be due to the fact that these 2 studies used 75% 1RM and 60% 1RM resistances, respectively.

Researchers at Cal State Fullerton wanted to investigate the EMG levels of the arms and abdominals while performing a chest press and shoulder press on an exercise ball at 80% 1RM. They recorded EMG levels of the anterior deltoid, pectoralis major, and rectus abdominus during 4 conditions: chest press on and off an exercise ball, and overhead shoulder press on and off an exercise ball. Subjects performed 3 repetitions at 80% of their previously determined maximal strength using dumbbells.  The resistance levels were the same between the stable and unstable conditions for each type of lift.  Muscle activation was normalized to their maximal EMG levels during the maximal strength testing. The researchers found no significant difference between the conditions: both the exercise ball and stable surfaces produced similar muscle activation levels at the same resistance levels.

It’s important to remember that this study used higher loads than previous studies. The authors hypothesized that EMG levels would be similar between stable and unstable conditions because of the stabilization of the ball caused by its deformity as a result of the subject’s body weight and resistance load. This suggests the exercise ball surface may have become more stable, comparable to a bench surface. Because the researchers did not control for the deformity of the exercise ball, more research is needed to determine if this was a reason for a lack of difference between conditions.

Based on the results of this study, the use of an exercise ball does not increase or decrease EMG of the shoulder or trunk muscles during the chest or overhead press at high loads.

Reference: Uribe BP, et al. Muscle activation when performing the chest press and shoulder press on a stable bench vs. a Swiss ball. J Strength Cond Res. 2010 Apr;24(4):1028-33.

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Anterior cruciate ligament (ACL) tears

Initially, Dr. Herman published a study concluding that while the protocol was effective at improving strength, the biomechanics of the athletes remained unchanged. He concluded that strengthening alone was not sufficient, and set out to find what needed to be combined with the training program. His subsequent study combined the Thera-Band strengthening protocol with video-assisted feedback, and he compared the combined intervention to a group receiving feedback only. Dr. Herman and his colleagues found that the group receiving both feedback and strengthening improved their biomechanics more than the feedback-only group. The paper won the 2008 O’Donoghue award from the American Orthopedic Society for Sports Medicine, given to the best overall paper that deals with clinical based research or human in-vivo research. While the Thera-Band training protocol combined with video feedback improves lower extremity strength and biomechanics in female athletes, research must determine if the protocol is effective at actually reducing ACL injuries.

Herman DC, et al. 2009. The effects of strength training on the lower extremity biomechanics of female recreational athletes during a stop-jump task. Am J Sports Med. 37(7):1301-1308.

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NEW YORK (Reuters Life!) – Call them Swiss balls, Pilates balls, physio balls, exercise balls, balance balls, yoga balls or body balls.

Stability balls by any other name would still be the same hardworking multi-taskers of the fitness world.

“They can be used for balance training, for core training, with or without weights and for resistance training,” Dr. Christina A. Geithner, of the American College of Sports Medicine, said of those big, colorful spheres that brighten the corners of workout rooms everywhere.

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Related Link: WebMD offers more information on safe exercise and pregancy.