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In the comments section of an earlier post that mentioned the potential caloric benefits of standing as opposed to sitting, Peter asked how sitting on an exercise ball stacks up. The news is good. A 2008 study in the European Journal of Applied Physiology by researchers at the University of Buffalo compared energy use during clerical tasks while sitting in an office chair, sitting on an exercise ball, or standing up. Subjects burned 4.1 calories more per hour (a 6% boost) when they were either standing or sitting on the exercise ball compared to sitting in the regular office chair. There was no difference between standing up and sitting on the exercise ball. The numbers are consistent with a 2006 study that found a 3.9 calorie per hour (5.6%) boost for exercise balls, with effects that persisted for at least a week.
Presumably, this enhanced calorie gain has the same benefits as standing — that it doesn’t trigger your appetite hormones to make you compensate. On the other hand, some back experts are still cautious about the effects of sitting on exercise balls all day. Stuart McGill of the University of Waterloo, for instance, did a study in 2006 with the following conclusions:
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.
So, as long as your back doesn’t start bothering you, the exercise ball seems like a reasonable choice. And you don’t have to worry about your productivity, at least according to the University of Buffalo study: in 20 minutes, the men in the study typed 551.8 words on the exercise ball, 535.6 words while standing up, and 519.2 words while sitting in the office chair. (The women were much consistent, at 700.3, 697.8 and 702.5 respectively.)