Since the introduction of ergonomic guidelines in the design of office chairs, a lot of effort has been put in designing these office chairs accordingly. Because these features all have to be adjusted in different ways (mostly a knob underneath the seat surface), and because every office chair offers different solutions, often users do not use all of the adjustments, and thus do not use the office chair an the optimal ergonomic way. http://www.newtral-chair.com/office-chair/