Does sitting on a gym ball at work increase your core stability? Does it increase energy expenditure? And most importantly, does it reduce incidence of back pain or improve posture? Well we at Zoinomics are firmly in the 'leave gym balls in the gym' camp, but lets look at the evidence...
Improving core stability: A study in 2006 in the Clinical Biomechanics Journal concluded that sitting on a gym ball produced no difference in trunk muscle activation than simply sitting on a surface without back support (i.e a bench or stool) and a more recent (2013) systematic review of a number of studies investigating the effect of dynamic sitting on trunk muscle activation in the Journal of Applied Ergonomics concluded that there was no increase in trunk muscle activation with dynamic sitting in 5 out of 7 studies. Of the other 2 studies, one showed increase muscle activation with dynamic sitting but only in one out of eight muscles measured and the other showed increased muscle activation but also increased 'spinal shrinkage', indicating compression of the discs in the spine and increased pressure. So with regards to improving 'core stability' - not likely.
Increasing energy expenditure: A 2008 study in the European Journal of Applied Physiology showed that energy expenditure increased when sitting on a gym ball compared to sitting on a chair. By how much? Around 33 calories per day!!! The equivalent of about half a medium size apple. A 2011 study in the Journal of Preventative Medicine, showed no difference in energy expenditure between sitting on a gym ball and sitting on a chair. So can we burn more calories sitting on a gym ball - not many, if any.
How about posture: (surely a gym ball forces me to improve my posture)? A 2006 study in the The Journal of the Human Factors concluded that prolonged sitting on a stability ball does not greatly alter the manner in which an individual sits, yet it appears to increase the level of discomfort. So same postures but increased discomfort? I guess not.
So, what are gym balls for..... Exercise, rehab, strengthening. They are gym equipment and can certainly help you to be fitter, stronger and more injury resistant, they can help to push you towards the positive end of the health and wellbeing spectrum that we all live on but the principle of good workplace/office ergonomics is to minimise physical demands and musculoskeletal loading and reduce effort. If workers are increasingly overweight, unfit and/or generally inactive, trying to 'force' increased activity by increasing postural demands is ineffectual at best and detrimental at worst.