Epidemiologists have known that static sitting is bad for people for some time now, and it’s become clear that static sitting on conventional chairs causes at least two different sorts of problems. First, sitting in conventional chairs requires that anatomically unusual postures be held for protracted periods, postures that can cause stiffness and contribute to back discomfort. Additionally, the core muscles are put at rest by static sitting, leading to deconditioning of these muscles that sets the stage for back injury and chronic pain. A second problem with conventional chairs is that sitting in these chairs causes most of the muscles in the body to “go dark”, that is, become metabolically inactive. This results not only in a decrease in the number of calories used, but a fundamental change in our basic biochemistry, resulting in deleterious cardiovascular and metabolic effects: increased blood pressure, increased levels of fasting glucose, triglycerides, and high-density lipoprotein are all associated with static sitting. There is some good news, however: It turns out that even modestly increasing the amount of activity involved in sitting may have large benefits: a recent study found that those who simply fidget while sitting are largely protected from the harmful metabolic consequences of sitting. Why “Ergonomic” chairs are bad for your posture.