To really deserve the label “ergonomic”, furniture and in particular chairs need to fulfill certain requirements. Some of the definitions of what makes a chair an ergonomic chair can be found at the website of the National Institutes of Health at http://www.ors.od.nih.gov/sr/dohs/HealthAndSafety/Ergonomics/Pages/ergonomic_chair.aspx.
It starts with the requirement that such type of furniture must be easily adjustable. If you read the above site you can see that it starts with the casters and the base of the chair which should make it possible to easily move to chair around when required.
The next aspect that needs to be looked at in regards to ergonomic chairs is their seat pan. The seat pan must support the person’s weight and it should also provide adequate cushioning. Ergonomic chairs usually slope forward which is also referred to as waterfall design. This serves the purpose to reduce pressure on the back.
The backrest is another important aspect of ergonomic chairs. The most important thing here is that the backrest provides adequate support and it must also be adjustable in various ways.
You can read more about ergonomic furniture here at http://www.spine-health.com/blog/9-ergonomic-tips-synchronizing-your-work-station-and-office-chair