I'm moving soon and I might actually have room for a desk for the first time in four years (YIPPEE!), so I started looking at desk chairs and came across stability ball chairs. I was seriously considering getting one until I thought to look up any research that's been done on the potential benefits of these chairs.
Below is an abstract reviewing seven studies on the effects of sitting on an exercise ball chair vs. a standard office chair. TL;DR: Stability ball chairs are associated with increased discomfort and do not provide clear benefits for trunk muscle activation.
So it looks like Jim was doing Dwight a huge favor when he did this:
Appl Ergon. 2013 Jul;44(4):628-35. doi: 10.1016/j.apergo.2012.12.006. Epub 2013 Jan 29.
The purpose of this systematic review was to investigate the effect of dynamic sitting on trunk muscle activation in sitting. Electronic databases were searched by two independent reviewers. Studies were included if they compared the effect of dynamic sitting on trunk muscle activation to a more static sitting condition. Seven studies were eligible for inclusion, six of which were rated as "high-quality" using the PEDro scale. Five studies reported no difference in trunk muscle activation. Two studies reported a difference in trunk muscle activation, yet this was associated with increased discomfort, increased fatigue and greater spinal shrinkage. Furthermore, the changes reported in these two studies may be more related to the absence of a backrest rather than dynamic sitting. Therefore, the findings of this review suggest dynamic sitting does not significantly change trunk muscle activation. No randomised clinical trials or longitudinal design studies were found which evaluated the effect of dynamic sitting on trunkmuscle activation, limiting the ability to make definitive conclusions about causality. The implications of the results, and recommendations for future research, are discussed.
Copyright © 2013 Elsevier Ltd and The Ergonomics Society. All rights reserved.