Sitting on an exercise ball is no more stimulating to core muscles than sitting on a chair

For years therapists and trainers have been encouraging their patients to sit on exercise balls as a form of therapy.  It had been thought that this activity stimulated the muscles of the core (namely the multifidus and the transverse abdominis muscles).   Researchers from the University of Waterloo put this notion to the test* and found that sitting on a ball was no more therapeutic (at least in regards to activating the deep muscles of the core) than sitting on a chair.  While more studies would be helpful in understanding the principles of balance and core muscle activation, this study dispels the notion that sitting on an exercise ball is a sufficient therapy for exercising the muscles of the core.

*Clin Biomech (Bristol, Avon). 2006 May;21(4):353-60. Epub 2006 Jan 10.

Sitting on a chair or an exercise ball: various perspectives to guide decision making.

McGill SM, Kavcic NS, Harvey E.

Clinical Biomechanics, Department of Kinesiology, University of Waterloo, Ont., Canada. mcgill@uwaterloo.ca

BACKGROUND: Prolonged sitting is recognized as a risk factor for the reporting of low back troubles. Despite the use of exercise balls in replacement of the office chair, little quantitative evidence exists to support this practice and hence motivated this research. Given the potential for several biological effects and mechanisms this study was approached with several layers of instrumentation to quantify differences in muscle activation, spine posture, spine compression and stability while sitting on an exercise ball versus a stable seat surface. Also, differences in the pressure distribution at the seat-user interface were quantified for the different seat surfaces to provide an objective perspective on the mechanism influencing perceived comfort levels. METHODS: Eight male subjects volunteered to sit for 30 min on an exercise ball and on a wooden stool. Muscle activity and spine position were used to model spine load and stability. An additional seven sat on an exercise ball and chair to examine pressure distribution over the contact area.
FINDINGS: There was no difference in muscle activation profiles of each of the 14 muscles between sitting on the stool and ball. Calculated stability and compression values showed sitting on the ball made no difference in mean response values. The contact area of the seat-user interface was greatest on the exercise ball.
INTERPRETATION: The results of this study suggest that prolonged sitting on a dynamic, unstable seat surface does not significantly affect the magnitudes of muscle activation, spine posture, spine loads or overall spine stability. Sitting on a ball appears to spread out the contact area possibly resulting in uncomfortable soft tissue compression perhaps explaining the reported discomfort.

PMID: 16410033 [PubMed - indexed for MEDLINE]

http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=16410033&dopt=Citation